Why do people think at all atheists are evolutionists?

idk

Because 99.9999% do. When you have a figure like 99.9999%, it's just easier to round up to 100% when speaking on the issue.

I don't expect an atheist to believe a god did it...

For the same reason that people think atheism is a religion: https://www.atheists.org/activism/resources/about-...

Antitheists evangelize Evolution, (among other doctrines), while claiming to be atheists: https://en.wikipedia.org/wiki/Antitheism

Antitheists do this, because they have been indoctrinated to believe that they're atheists, even though atheism doesn't have beliefs to evangelize.

Evolutionists?

So do you refer to people who accept gravitation to be gravitationists?

Because people think those two things go hand in hand

because most glorify evolution

Most people don't know what atheism means.

Evolution belief is required in Atheism. No Evolution = no Atheism

I haven't met any that aren't.