Personally, I love Spongebob; I don't regard him as annoying, I think he's hilarious. He's one of my favorite characters. He's also one of the most popular cartoons, very successful. So he makes the most obvious choice, along with Simpsons, for Universal Studios to focus on. It's all about the money. They need money to continue making their stuff, so they focus on something that will make them a lot of money. And seeing how popular Spongebob and Simpsons are, they make the most likely ones to pick. And selling merchandise is a major way Universal brings in money, so it makes more logical sense to pick something more successful than something that isn't.
And anyway, from what I recall, I'm pretty sure Nickelodeon is, in a way, affiliated with Universal Studios. During the ends of some programming (live action ones) I do recall them always saying "Universal Studios"..in Florida I believe. This is probably why Spongebob is showing up in Universal Studios. However, it doesn't really explain The Simpsons, since that's Fox, isn't it? Perhaps Univeral Studios bought it or something. I dunno.
And anyway, what could we do? Say that we don't like Spongebob and that we want LBT back? Sorry, it's not going to work; as I stated before, Universal, like other major companies, are going to want to focus on something that is very successful, in stores and TV and such, and Spongebob is one such popular show. LBT, on the other hand, is apparently not making enough money for them to continue focusing on it.