If these “things” are so advanced, how come they crashed?
It’s the asteroid belt... the odds of safely navigating it are 3,720 to 1...
The very same question can be asked of those fancy-dancy F35s, only 100 miles from home.
Besides, their mode of travel may not be so esoteric, just something we don't know about at this time. The natives of Micronesia literally worshiped the C-47s and their crews; and, those weren't out of the reach of understanding. They were just something they didn't know about.
And apparently repeatedly and with regularity...and given it is “multiple species” - happening with multiple advanced civilizations - all with the technology to be able to travel interstellar and/or intergalactic space then suddenly for all of them, and multiple craft, lose control and crash when they come here.