Because it doesn’t take 100s of years?
There are thousands of credible witnesses who have witnessed what they call ships, and this over a span of many years. Is it more scientific to find reasons to justify ignoring those objects, or to find reasons for their presence? Just because we don't know the "how" or "why" of events doesn't mean the events never occurred. I choose the latter approach because it is more in keeping with good science.
To that end, one conclusion that must be strongly considered is that "the others" know things about physics we don't. I was a high scoring physics major in college.