>>118452970 The Maitlands basically become Lydia's surrogate parents and (ironically) life coaches at the end of the film.
That's a good story conclusion but it's a little complex for a kid's cartoon, let alone one that came out at the tail end of the 80s to have Lydia hang out with two sets of parents and then try to explain that. Or even have her biological father and stepmother be portrayed as film accurate and not really understand/care for her.
And since the cartoon's named after him, I can see the thought process to turn BJ from the villain of the movie into a sort-of hero who's juuuuust mischievous and spooky enough to get away with some of the same scare people shit from the film but with a measure of goodness to allow him to be a legitimate protagonist in the series.
Alot of the earlier episodes sort of had a moral instilled in them, whether he or Lydia or both were supposed to learn it, but again, they still kept him enough of a rascal so you knew that the lesson probably wouldn't stick.