I know this has been mentioned before, but isn't it so weird that Eggman programs emotions and personalities into his robots??
People point out that this is really self destructive on his end because it can lead to some of his creations turning against him after building resentful emotions toward him, like Omega, Gamma, and all of the robots on Scrapnik Island.
My personal headcanon behind his thought process is that not even pure mechanical obedience can rival the loyalty a creation will have to its creator, or "father." It doesn't matter if you reprogram or rewire its entire structure to have its own free will if it's inherent personality, aspirations, and deepest desires will always be to make eggman proud of them, because of the way he's designed and conditioned them. They'll always return to him no matter how many chances you give them, because he's made it so that their biggest desire is to make him proud, even when given free-will or reprogrammed.
We see this most clearly with Metal Sonic, and Sonic will even tease him and take digs at him for it in the comics, telling him to "run home to daddy" (cringe). Clearly, even the characters in-story can see how eggman has raised all of his creations to depend on him for any sense of self worth or purpose. Truly evil, and I think something that's always overlooked when discussing eggman. People say he's not a respectable villain but I think this is really compelling and a unqiue way for a villain to function. Especially because his design is pretty dad-like to begin with, with the mustache, glasses, round body, and bald head lol.
It's so effective, that even when Metal Sonic gains even more power than Eggman through becoming Neo-Metal, he still only wants to take over the world to gift to Eggman. His influence even goes past his creations and gains loyalty from other aspiring inventors, like Dr. Starline.
Most of all, I think it's so effective because it's genuine. He really does love his creations, but simultaneously holds them up to impossible expectations and holds severe disappointment in them when they fail. I mean, think of it. Isn't it awful to design a creation that entirely depends on you for any feeling of worth or purpose, and to make it capable of love and such, only then to neglect and abandon it when it doesn't live up to your impossible standards? Just think of Scrapnik Island and the sheer amount of abandoned bots there.
I think after seeing Mr. Tinker and Belle, it raises the question, does Eggman deep down just want to foster these fatherly connections? To build childrens' toys and fun-rides and kiddy amusement parks, with his helpful heart-filled robot creations? He does often say that he only wants to take over the world in order to "enhance it" with technology, and that people just aren't cooperating. Maybe somewhere down the line his pure intentions got corrupted somehow into this extreme need for absolute control.