I always love seeing your takes on how Eggman being Knuckles' first friend and then him betraying him has such a deep effect on Knuckles. Like Eggman showed up on his island and not only showed Knuckles that there really was something beyond his island he also let him know of an incoming attack which would've allowed Knuckles to feel that he was fulfilling his purpose. and then on top of that it's very likely that Knuckles would've been open and shared so much with Eggman because he's had literally no contact with anyone ever. Eggman's betrayal cut this boy so deep that the scars of what he did are gonna stick around forever and there's just so much to explore and think about. So much of his character gets so much more depth and complexity with just that fact alone. I could go on and on about the Knuckles eggman dynamic and i think its criminally underexplored both in canon and fandom.
Oh it's definitely criminally unexplored and I think people need to acknowledge that Eggman both was Knuckles' first friend and his first interaction with betrayal. As someone who's been through that (friend betrayal), it's fucked up and it jolts your sense of righteous anger and injustice that I think Knuckles would definitely hold after the events of S3&K.
But he also holds hope that the Doctor can change. It's only in later games that he starts to adopt Sonic's attitude towards Eggman and abandons it a little but he seems to, briefly, try to believe in him. It's why he's gullible towards his actions and warnings in later games - he wants to hope that that was a one off but it becomes two offs, three offs, and Knuckles only has so much trust to give until it's down to three people.