I am going to talk about where and when Elias Diner was founded and different animatronic if you interested in lore, let's get into it.

Opening Day

In 1984, two friends are planned a business venture to create a new restaurant because they thought 1984 would be great for that time. The construction was completed and it was called Elias Diner to sold pizza and with the attraction being these 6 animatronic.

Quick Problem

Elias Diner ran into a quick problem when theres an accident with someone accidentally tripped an animatronic named Titi and disfigured his face. He had to wear a mask so he wouldn't scare children.

Later, the other animatronic named Nick starts to be underestimate due of a problem that he is afraid of human and never amuse them for entertaining. They don't know how to solve this problem so they decide to put Nick stay in his room.

Accident

Billy, one of the owner for Elias Diner, starting to left in silence without another owner (his best friend) and haven't had a conversation in a while due of their problem. Billy were consumed by his feelings that it drives him crazy that he attacking his best friend's family and him. Billy stabbing him and putting him in Elias suit.

After the accident, the worker and people occurred that in Elias suit had a strange smell of the dead and they somehow doesn't know the animatronic were possessed.

Bankrupt

Elias Diner started to get occurred that left the resturant bankrupt due of what was happened in a night. Elias had supposedly to move from his stage for no reason and went to power room and a camera saw what happened is that the man disappeared and the other animatronic were destoryed.

The police arrived at the scene and they saw that Elias began to spill liquid on his head in recording, lead to began to investigate the chaos. After the investigate, Elias Diner closed its doors forever and (I think) the worker throw Elias in an abandoned alley.

So that will be all for this theory, let me know in the comments if theres anything I have missed or wrong!