A lot of scientific insights are obvious in hindsight. IMO especially in applied mathematics, but maybe that's just because it's a field I know well enough to notice.

A lot of ideas are obvious even without hindsight (again, especially in applied mathematics, and again, maybe that's just my bias). None-the-less, the person who said it first gets their name on the important idea.

There are lots of "<person's name> operator" and "<person's name> theorem" in big-but-not-core fields of (again, esp applied) mathematics where this phenomenon occurs.

I've been party to a lot of conversations that go something like "<person's name> idea or <person's name> technique is just '<fairly basic thing> applied to <fairly commonplace thing>' and it's stupid that it's named after <person's name>".

I always remind the speaker that this is good news -- one route to science fame is to just state the obvious loudly enough and early enough ;-)