honestly, that's my thought. i think it's so heavy handed that he's a bad guy in a reverse psychology kind of way. here's my theory, though maybe i'm just off my rocker. i think marvel is banking on people knowing who mysterio is, and those who don't will ask others who do. it's a wasted reveal. marvel has a tendency to show false information in their trailers so it's weird to show mysterio in this light when it's OBVIOUSLY misleading.
my thought is that mysterio isn't pretending, he actually does have powers and actually WANTS to be a hero
This is often a much better way to handle a character than the blatant "he's evil!" approach. I have hated Jake Gyllenhall since Donnie Darko, but hopefully they do what you guys are suggesting with Mysterio, and despite my hate I know JG can pull it off. That's why Michael Rosenbaum's Lex Luthor in Smallville is one of my favorite villains of all time. Sure, they had him do stupid or "evil" shit occasionally, but by and large he was always trying to do the right thing, he was just cutting corners a true "hero" wouldn't have, or getting caught up in situations he shouldn't have, etc.
This scene is one that always stuck with me. The Kent family had been kidnapped, and Clark had begged Lex to do whatever it takes to save them. I forget the specifics of the episode, but I think the kidnapping was tangentially caused by shitty things the Luthor family (probably his dad, Lionel) had done, that Lex might not have even been aware of. And something about the rescue ends up making Lex look bad, I think, even though he was only trying to help his friend. But the difference between the happiness and love that the Kents have is starkly contrasted with the shitty family Lex has, and was a perfect example of yet another way that Lex tried to be good and heroic and rise above, but things around him constantly pulled him back down. That is what made this version of Lex the best one that's ever been portrayed, in my mind, instead of the ones that are evil just because.
Might not make a lot of sense when you watch it as a clip, but it was extremely powerful the first time I watched it on TV.