To answer your first question of "How come Peter Parker be what the movies had made him do?" They made him do because that's how studios make money, your welcome.

@LunchGoddess I meant in each movie Peter has to deal with the dilemma of losing and sacrificing everything he has and cares about. Did you read the first paragraph?!

@Jon825lazery7 Yeah I read the whole thing, just a quick recommendation, double check your spelling before posting if you want me to understand you.

Peter Parker is known for being a tragic hero. That’s not to say other heroes have not suffer lost as well. The films, even non MCU films, have noted that as well. 

As for the spell, a common thing come up for Doctor Strange is the question of “Was that the only way?” Could they done the original spell differently? Probably, but Peter focus was on people forgetting he was Spider-Man, not forgetting about Mysterio and his actions. Strange seem to following Peter’s request.