Summary: There's been a lot of speculative ideas put forth about the Multiverse, and I dare say that a great many of them are nothing more than wishful thinking. But that doesn't mean the Multiverse itself is ill-motivated at all. Rather, if you take two of our best theories that have been well-confirmed in a wide variety of different ways, you're going to find that you arrive at a bizarre but unavoidable picture: one of an inflating spacetime, eternal to the future, where regions that look like our Universe, complete with a hot Big Bang, are spawned continuously. The evidence might not be there, observably, to confirm or deny the existence of a Multiverse. But as a theoretical consequence, it certainly has a motivation that's far stronger than practically anyone realizes. Here's the cosmic story.
