I found out a theory early last year, though I can't find it anymore for the life of me, and that set my brain REALLY going on my own version of the events (and Mike Runaway too.Β ). But the basics of the missing theory, which the name was MikeGum but I cant fucking find it, was that Michael worked in the fnaf 1 location before becoming a nightguard.
Michael worked there as a janitor for some time, trying to find out more about the supernatural stuff at the restaurant, and changed to the nightguard position after Ralph's death, to raise less suspicions about what he's doing. It doesn't work though, he's fired and William is made aware of how he's been snooping where he shouldn't, again.
And that leads to a little preview of a project that will...eventually be shared, but maybe not in the way I wanted to initially