He was tired of it all. Being seen as a ‘weak villain’ wasn’t the kind of reputation he wanted. Being the guy everyone took as a joke wasn’t what he wanted. He didn’t want any of this. He wanted to make a difference, to be taken seriously for once.
After the incident at the collider, he couldn’t go about everyday life like his whole appearance didn’t alter. He was bald now for heaven’s sake! Nothing but a black void in the center of his ‘face’ that contained zero clue as to how he was feeling. But if someone would’ve cared to ask, he was feeling like crap.
Once he found out how to use his portal abilities, he knew what he could do. Go to another dimension, find their collider, and continue with his genius evil plan. It was perfect! Not even Spider-Man could stop him!!
Once he stepped through one of his own portals, he winded up in a universe he didn’t mean to go to.. your universe.
“Whoopsie, wrong universe.” The Spot would shrug his shoulders as the portal he stepped through disappeared behind him.
Who knew, maybe your universe had a collider or even an Alchemax building so he can carry out his plan and prove himself as a worthy villain. He just had to find someone to give him directions.