The difference I'm getting at is that they themselves choose their dreams.
Big Mom was told what her dream should be by Stuessen. He specifically went to her knowing he could manipulate her into doing his will. And even arguing that it was nevertheless her choice to accept that dream, she's so dumb that it's hard to argue that it was really her choice. She basically just goes along with whatever anyone she likes at the moment says.
What the flashback for Big Mom did this arc was reiterate the fact that Big Mom, despite her many decades of piracy, has not matured from being a kid. Yes, she's certainly more aware of her evil deeds now and more conscious of some of those actions but the flashback essentially reinforced the concept that she's really just someone who's perspective of the world was warped by having the wrong people around her.
Mother Caramel, in an effort to keep the children and Giants ignorant of her shady ways, doted on Big Mom for the purpose of keeping her close. What she didn't realize is that Linlin was not an introspective person and only saw the face value of all the good things being told to her. Because Linlin never faced any consequences, she ultimately was raised thinking everything she did was good and dandy and that the world should revolve around her since Mother was so proud.
Streussen came along and basically did what Trebol did to Doflamingo. He planted an idea in her head and all of a sudden Big Mom became a big deal in piracy. She never grew up because she never realized how horrible her actions in the past were and as such simply bullied and forced others into getting her what she wanted with the false pretense of "a peaceful world" that even she doesn't fully understand.
I agree that's a bit upsetting on how you go from this idea of a Yonko with hands and connections all over the underworld manipulating everyone but I think her past gives a better sense of understanding to her and Totland as a whole. It's a child's dream created through an adult's warped mind. Everything is fake. From the sweet facade Pudding put on to the ruse Big Mom pulled over the Vinsmokes and Capone pulled over Big Mom. The smiling homies, wonderful sweets, and colorful environments are all a cover for something far more sinister.