Since when was the multiverse debunked? I'd also like to see a good, reliable source confirming that the concept of the multiverse was invented specifically to support the atheist position. Take note that I'm not talking about modern atheists using it as justification for their beliefs, I am asking for evidence that the first person to come up with the idea had purely atheistic motivations for doing so.
well OK, static, steady state, big crunch were debunked. Multiverses, M Theory etc are of course inherently beyond the inconvenience of scientific investigation.
Hawking, Greene are principle proponents of multiverse and both atheists. Hawking always insists his theories make God redundant- Greene has talked about the possibility of our universe being intelligently designed by some alien intelligence (but not God of course!)- but this latest atheism of the gaps argument against God is becoming increasingly pedantic/ semantic.
The origins of parallel universes goes back beyond recorded history, so looking for a record of their indented implications of it, is about as practical as looking for multiverses themselves.
But obviously a multiverse is the latest atheist explanation de-jour - and probably also the last. An infinite improbability machine was always going to be the last resort after anything remotely testable had failed