You'd think that movie-makers would know why we loved the movie the first time and give us more of what we want. You'd be wrong, and a lot of these sequels jettisoned what we liked and replaced it with truly awful dreck.
It's also possible that this was supposed to be the script of another movie entirely and they wound up taking that script and making it the sequel. Or, the studio just didn't care about the integrity of the franchise and just saw dollar signs, figuring that the general public would pay to see an awful sequel.
Sadly, that last one has proven itself true again and again, which is why we can't have nice things.
