I think you have identified the purpose of such theory... to discredit the existence of God.
Just like evolution and time travel.... it’s all linked together.
It is fed to us on a daily basis NOT just through science, but through entertainment as well in the form of science fiction.
Parallel universes, time travel, and evolution has been the core plot basis for Star Trek and so many others like it...
The logic of such science sounds much more palpable to our brains because it is so far beyond us, and special effects brings it into our visual reality... but for anyone who believes in God, it becomes utter nonsense for the very reasons you stated... It would all make God out to be someone who IS NOT INVOLVED in His creation.
I wouldn’t count parallel universes and time travel out quite yet.
Bingo. The multiverse is Atheistic science fiction with no hard science (empirical evidence) behind it.