Whoever wrote the letters supposedly written by "Paul" that made their way into the New Testament before someone said, "Hey, wait, Paul wrote in Greek a lot better than this!" went for the big guns. There is a also Gnostic Gospel of Peter, of James, of Philip...the list goes on.

However, you seem to be disregarding the entire second paragraph of what I wrote. The gospels circulated anonymously for some time, and when people started putting names on them to attribute them to someone, they based it on their understanding of who wrote the book, rather than intentionally lie to increase the book's popularity. The text was already accepted, and there was likely an oral tradition about who might have written it. The oral traditions around the four canonical gospels determined their attribution, and the same is likely true of Thomas and a few of the earlier Gnostic works.

Some of the later attributions might be the result of competition and lying, but of the canonical gospels Matthew might have gotten its name in the same way, given the late date of its attribution. The people who stuck the name on top might even have wanted to use someone else's name, but that name was already taken.