So what motivated the lore change?
damn this is a month old uhhh 😭 as a preamble for anyone interested, i haven't been on this blog for ages bc of college and i just haven't been in a fnaf headspace for a while. so yeah 👍 but to answer your question uhhh
short version: probably watching the fnaf movie for the first time? matthew lillard was good in it 👍 and then i read his empire of dirt by pearlandpine on ao3 and all related fics by them. and i already wanted to make my au more original and more of My work as opposed to sticking very closely to the parlourverse by @/fivenightsatfreddysfanfiction
long version: as someone whose tastes are pretty "oldschool" when it comes to fnaf and fnaf aus i sort of ended up avoiding the movies. i like the ambiguity and freedom, as well as the complete-feeling story, that fnaf 1-3 have. plus i have something of a kneejerk aversion to the almost. stereotypical "william afton" concept (it's hard to describe. i just don't prefer him or michael afton being the main character tbh). the idea of remnant also just flat out does not interest me, because i feel it's pulled fnaf away from a horror and straight into paranormal-science fiction. but i digress.
anyway the fnaf 2 movie came out and it was kind of a "why not?" thing. despite my previous paragraph i do actually find newer fnaf to be fascinating from a distance, seeing how it evolved. i don't hate it; it's just never been for me. but i watched the fnaf 2 movie for my 10 year old self and honestly it was a decently fun time! but it was like a solid 6.5/10 for me so i figured that some points were lost because i didn't have the extra context from the first movie.
so i watched it. and then it was SO much better that it dropped the fnaf 2 movie down to a 5/10. let it be said i am a huge sucker for sibling dynamics in fiction, especially when they're kinda dysfunctional about it and/or one has to raise the other. AND when the caretaker also hung up on the death of a previous sibling and blames himself for it. it's so lucas it's crazy. ahem. also vanessa took a bit more time to digest for me but when she did. holy fuck. oh my god. [explodes]
and the novelization was even better than the movie (i process things easier through reading compared to watching) and it made me start kicking myself because i could've gotten here much much earlier if i opened my heart to it all. etc. and also like i said earlier matthew lillard did a pretty good job and i like how his face moves. he added a bitchy pettiness to steve raglan that i enjoyed. i still dgaf about william afton though but it made me more receptive to new ideas.
and then at some point, thanks to some gorgeous fanart that i can't find anymore, i stumbled across a link to his empire of dirt by pearlandpine on ao3 which is a fic where michael time travels to his father's past and tries to change things. you should absolutely give it a shot if you like michael and/or william afton. i did not start out fond of either but i ended up incredibly endeared to michael nonetheless and his struggle to come to terms with the fact that he still deserves love despite everything. and william's own struggle to become a better person really resonated. the flashbacks to the "original" timeline and seeing the intersections between the future and past williams were also very interesting to me.
anyways all this to say these things warmed me up greatly to the concept of william afton. and then like i said i was also wanting to change lucasverse to be more original in concept/story because i was and have been largely piggybacking off the work of the parlourverse. i mean i grew up with it and lucas has always been an oc from there, and i've just been nostalgically fond of the characters and everything. but it's always felt very Awkward building lucasverse with the parlourverse blocks because i was using someone else's original characters and breaking them apart and twisting them to fit my mold. with fnaf as a whole, scott cawthon isn't going to see what i do with the outline of his story and also i don't respect him. with the parlourverse... i mean i know and have talked to avec before 😭 it just feels awkward to use someone's oc as free real estate. yk how it is.
so anyways all of this led to me deciding to rehaul the au and use the afton family as my new touys to squash and stretch and decapitate. so yea hope this answers your question 👍