A thorough analysis on Molenoid history
I believe that the Molenoids' motto "ignorance is bliss" comes from them viewing their excellent memory as a curse.
In "The Hard Part", when Trixie lost the map of Deep Storage, Pronto assured the gang that he already had the map in his brains. It did seem that Pronto had led the gang to a dead end, but the fact that the Scrap Force knew what the gang was searching for and waited for them at the location they believed that the gang would find the Vitalis Crystal, I believe that Pronto did manage to lead his friends to the right place, albeit longer.
In "Keys to the Kingdom", Pronto drew a map to the Vault of Knowledge for the gang in just a few seconds. It is a brief map but it's pretty accurate. Since Pronto has not returned to Molemound for many years, it is impressive that he still remembers the route well. With that, I can see that Pronto has an extremely high memory, and this trait might be inherited in all Molenoids.
Unfortunately, having an excellent memory can be a curse. Even when the maps were destroyed, the bad guys could kidnap and torture Molenoids who had seen the maps since they have excellent memory. You can have the knowledge of the entire world but you can't have peace. It is an awful trade off. That's why they choose ignorance over wisdom.
To protect its people, the king of the Molenoids might have ordered the construction of the Vault of Knowledge so they could store all their maps and records there and seal them away. As time passed, the Molenoids who had seen those maps and records grew old and later passed away. They could still orally pass down what the Molenoids have like the Mapa Mundi to the future generations, but the future generations have no idea what they look like and the older generations took those visual information and memories to their graves. With that, the bad guys gradually stopped bothering them, and the Molenoids are safe.
However, the Molenoids take "ignorance is bliss" too far to the point that majority of them become too dependent on their king. Of course, the minority of them are rich and highly educated, even some still continues their roles as trackers. I believe that the kings generally consist of trackers because they have the knowledge and skills to take care of their people. By choosing trackers to be kings, they can also discourage them to go out exploring and force them to serve the people.
We know that a part of their rulebook has been sealed in the Vault of Knowledge, and I believe that it was done when they were sealing their maps and records. The rulebook does contain a rule that allows the king to choose a proxy when he's unavailable, and it may contain a rule about being eligible for the throne for having the most awesome slugs. I have a feeling that the king or the king's advisor that time decided to take out this part of the rulebook and hide it away so that they can assure that the future kings cannot find any loopholes to excuse themselves from their duties or to have anyone else to challenge the throne.
I like to believe that Pronto and Sedo's bitter rivalry comes from conflicting ideologies. Their families are well-off with Pronto's family having a long line of explorers and Sedo's family being rich. Sedo wants to use his resources to provide luxurious comfort and relaxation for his people, upholding their motto "ignorance is bliss". Pronto, on the other hand, wants to continue their legacy as explorers and trackers, and prefers that they should be more independent. Their rivalry might have extended to "who should be king" that time.
Ultimately, the king of the Molenoids that time chose Pronto to be his heir. We have seen a younger Pronto going on adventures in the slugisodes, including that time he "helped" the king to "retrieve" the stolen golden chalice. I feel that the king chose Pronto because he's more eligible for the throne.
I am sure that their rivalry got worse when Pronto became king. Sedo felt that he would be a better king but the king chose Pronto to discourage him from going out exploring further and wanted him to use his skills as an explorer to serve his people. Sedo became more bitter when Pronto ran away from his duties, abandoning his people to seek out "selfish" enjoyment. Without any rule to take the throne for himself and seeing the living conditions of his people deteriorate and their reputation gets tainted, Sedo decided to take matters into his own hands. He went outside and spent his resources to make himself look good in hopes that he could show everyone the perfect image of a Molenoid. He wanted to crush the negative stereotypes surrounding his people and make them likeable. I feel that he chose to work for Blakk because he wanted to use Blakk's resources to help his people like improving their living conditions.
Of course, Sedo was unsuccessful to catch the Crystalyd slug for Dr. Blakk thanks to Pronto, who he has not seen for a long time. Then, he offered to hand over the Mapa Mundi in exchange for his services. That time Blakk was planning to take over Slugterra and was interested in exploring unknown caverns like the Outback Reach, so he gave Sedo a second chance. He sent Nacho to cause trouble in Molemound so the gang must go there, forcing Pronto to go back home and reveal himself as the king to his people. Nacho baited the gang to the Vault of Knowledge so he could retrieve the Mapa Mundi while Pronto was stuck to serve his people, giving Sedo the opportunity to challenge him for the throne, and if he succeeded, he could do anything for his people.
Thankfully, Nacho didn't get the actual map and Pronto defeated Sedo to reclaim the throne. Eli got the real Mapa Mundi and suggested Pronto to destroy it. Pronto seemed to be upset that the Mapa Mundi was the last surviving record of Molenoid history but he agreed that destroying the map was the best choice for Slugterra and his people. Pronto took a look at the map and then let Burpy burn it.
I have mentioned that Pronto has an excellent memory, and this might be a trait for all Molenoids. Since Pronto has seen the Mapa Mundi before burning it, every information from the map is now inside his brains even though the physical copy is gone. This means that the last record of Molenoid history actually survives in Pronto's brains and he can pass it down orally to the next generation, the next heir or to his friends if he wants to. Even if Blakk knows that Molenoids have high memory and that he deduced that Pronto would have seen it as he is the only Molenoid to have seen the Mapa Mundi, he knows that he can't pry any information from Pronto due to his loyalty to the Shane Gang. Besides, as the only Molenoid that has seen the Mapa Mundi, Pronto technically is now the best tracker in Slugterra and this will satisfy his ego.
