All things being what they are, it is certainly reasonable for the builders to have been transients on this planet. Assuming that the equipment was not manufactured here certainly explains the lack of infrastructure to make it; and, why it would be best to pack it up when finished.
To my own way of thinking, I suspect civilization has risen and fallen many times on this odd planet. It is just irksome that more evidence cannot be found that would help us understand our history.
I'm of the opinion that more than enough evidence has surfaced to piece together the true story of mankind's distant past, but the academic community being what it is, much (if not most) of that evidence has been suppressed or hidden from the public.
What we're left with, is the evidence in stone, staring us in the face, and defying us to simply look, and engage our God given powers of reason to explain it.
Like you, it's my personal belief that civilization has risen and fallen over and over on this planet. The ancient oral traditions of many cultures even speak of it, but of course it's all dismissed as myth by the academics.