How would things be like if SpongeBob ended after the first movie back in 2004?
Well, for my theory, shortly after the first movie hit the theaters, Nickelodeon announced that SpongeBob SquarePants would be canceled for Stephen Hillenberg's wish. This upset many of the NickToon fans because SpongeBob was super popular, though they would eventually calm down since they still had The Fairly OddParents.
Even after SpongeBob's cancellation, it would still remain popular, especially since Nickelodeon would still be making SpongeBob video games. They would still make Atlantis SquarePantis, Truth or Square?, Sponge Out of Water, SpongeBob's Big Birthday Blowout, and Sponge On the Run.
Fast forward in the 2010s and The Fairly OddParents was declining in quality and popularity, and they knew they couldn't keep up with that show forever, so they convinced Stephen Hillenberg to revive SpongeBob SquarePants, and he agreed to do so. And what better way to revive an awesome cartoon is making a second movie.
SpongeBob is back on track, while The Fairly OddParents was declining even more, and The Loud House was on its way next year. Fairly OddParents eventually moved to NickToons so it can slowly die. And everything else resumed like normal, except SpongeBob Seasons 4-9a never existed, and that was my theory.