This sort of nonsense no doubt sells books and get's people speaking engagements but it's hardly real science and as others have pointed out is usually driven by a religious agenda.
It reminds me of simply trying to sweep dust into a pan, as you keep moving back the line of dust does too and you can never get it in.
Trying to explain how life began by claiming some other life must have brought it simply pushes the problem back ... so how did that life begin? Why is it beginning elsewhere, somehow getting into space, surviving a trip for millennia and also the entry into our atmosphere and impact somehow "more believable" as an explanation than the life suited for our environment developing in the environment.
You see the same crazy argument when it comes to even simpler things like "making fire". For some reason, some people believe that no one could ever have figured out or happened upon a way to make fire and that instead, some aliens must have come down and taught us.
So instead of simply needing a neanderthal capable of noticing something or accidentally discovering how to do it, you now need aliens and space flight and so on. Far less likely and ultimately not an explanation at all - because presumably, they needed to make fire at some point ... so who taught them?
Would anyone like to buy my book about the whole thing? ...