The multiple universe believe

The atheïst point of view on the finetuning of the universe is 'the blind believe in multiple universes without the slightest evidence for that'.. Ockham would not accept such amount of hypothesised entities to declare the finetuning of our universe. God requires less believe than a believe in multiple universes without the slightest evidence for such idea. So, why not say: we don't know. Why not be agnostic about it instead of coming up with a blind believe in multiple universes with other laws of nature.