In a way, it makes sense to me.
If the big bang was not unique - and why would it be - it makes sense that it would rather be infinite. It exists outside of time and reason, if it is not singular it doesn’t make sense to think that it only happened a finite number of times.
If it happened an infinite number of times, everything that could happen will happen in one of the instances. That’s just math.
So I guess I think it’s a reasonable idea.
However, I don’t know if it makes sense to me to think in terms of these worlds actually existing. After all, they are by definition not a part of our world, which I think would be a reasonable definition of existing.
I heard Stephen Hawkins was playing around with the possibility of connecting to other words. If that is possible, it would make them real by my definition of reality. I don’t personally believe such a thing would be possible. But I know far less about the topic than Stephen Hawkins.
That sounds like it would get very expensive very fast.