> However every once in a while the stars align and the new species fits into a slot the home team didn't "realize" existed, or they hammer a weakness that the rest of the ecosystem had just been coevolving around for a long time, and you get the invasive species.

"One thing that may help resolve this in your head is that" the echosystem might be destroyed, so an invasive species just takes the place of other species. Like, you know, we kill all the volves and then we are invaded by deers.