Thinking more about my UB-Family au so here are a few thoughts:
The current plan of the UBs is too take over alola with the Aether Foundation. To do that they have infiltrated various parts of the islands and started causing scenarios in which only the Foundation can resolve, creating trust in the public until they have the whole region under their thumb.
They accomplish this in many ways, mainly posing as a company devoted to helping pokemon in need, but they also claim to protect the region from outsider threats such as the mysterious Ultra-Beasts sittings around the region...
Ultimately Necrozma is the leader of the entire operation, controlling it all from the shadows... The second in command is Pherolusa, taking care of managing the specifics of the mission. Buzzglad is in charge of overall field operations, Nihilily is responsible for infiltration and Guzzmohn is the clean up crew.
The Tapus HATE the Aether Foundation, as they can sense that they are outsiders who pose a treat to the islands. As such they are currently one of the biggest adversaries to the UB-Family
The other main thorn on their path to world domination is the Ultra Recon Squad, they sensed Necrozma was up to something and have sent you (the player) to help understand what exactly is going on.