Yeah I actually forgot about Charlie's character.

My guess is that Lenkov just decided he was done with the character, and decided to unceremoniously drop him. Kinda seems like Lenkov treated the actors like furniture, which you just discard when you're done.

Now, this is standard practice in Hollywood (and extended Hollywood like the case here), but it kind of sucks for the actor who feels he finally got his opportunity, only to have it abruptly yanked away through no fault of their own.

I've even seen roles dropped simply because writers mishandled the character, and there was no place to go from there!