But temperature is not just the speed of a molecule right?

It pretty much is.

Like a molecule moving very fast through space can still be at a very low temperature, right?

That very much depends on the relative speed of the molecule and you. If you’re not moving in relation to the molecule, a collision between you and it won’t do much. Now try being hit by it (or a bunch of them) at high or even relativistic speeds. The area of you that’s hit will surely become pretty hot then.

Like, have you seen footage of asteroid impacts? Have you seen shooting stars? Those are hot. Like, non-figuratively.