Your question is valid because this was actually mentioned in the novel. They asked him about it. I couldn’t remember who asked but this very question was brought up and the butler answered it. I can’t exactly remember his answer but yeah it’ll be explained. Reading the novel, I was wondering about this too hahaha but I’m glad the author cleared it up.
Yeah, cause we can't just proceed with the story without clearing how the servant come to terms accepting Abel as his new master like, what exactly did he feel and what did he think when Lil just started spouting some things clearly only Melmont and Abel knew... and he's just there nodding as if he's also part of it too.
It was when Abel cut his hair. Abel came clean to the butler (because we all know Abel can't lie, especially to the people who have done nothing wrong) and said that he was not his young master anymore and that he was extremely grateful to him for letting him take over his body and that he will take care of it as much as he can (well he ended up collapsing several times but it's only because Abel didn't expect the body to be as weak as it was). Of course the Butler mourned his original master's death but he could see that Abel was a good person and since he's inhabiting his body, and with the original's parents' order, he chose to stay by his side. There are moments where the Butler forgets and slips seeing him still as the young master but no one could blame him because that body was his young master.
Karas and Lil (Abel) relationship aside... are we gonna ignore the fact how Lil's servant who knew the young master very well just accepted that his original master is gone and Abel is the new owner of that tiny body??....
Like think about it, if you were him and you've been with this gorgeous little thing, your master that you've served for a long time... then you find out the moment your master woke up, gawd knows whom it is that's using your master's body, wouldn't that make you feel a sense of confusion?? You would not be as chill as fuck knowing someone else is pretending to be your master. Does he think that perhaps, the you master suffers from amnesia from the brick of death??
But it surprises me and I'm quite amazed at the same time that he quickly accepted it and is just glad that at least, it may not be the real Lil on the inside, it's still the Lil on the outside. And going with the flow of everything, not even questioning why he knows some stuff like this and that. Oh the loyalty of a servant... Truly amazes me