Albert Einstein said "I like to think the moon is there even if I'm not looking at it".
I'm thinking the Double slit experiments could have been a major factor in his attitude towards QM.
https://en.wikipedia.org/wiki/Double-slit_experiment
"[T]he atoms or elementary particles themselves are not real; they form a world of potentialities or possibilities rather than one of things or facts."
Werner Heisenberg
Einstein arguments against QM now have been proven wrong, the world is not real,, so we have now the many worlds interpetation, with all propabilities happening in a infinite universes.