We simply don't know what came before the Big Bang. We do know what to expect from death - nothing.
If conservation of mass-energy, aside from short term Heisenberg tricks, isn't a physical law, then there aren't any physical laws. The get out of jail free card for the Big Bang is ... if there is no universe, then there are no laws.
There is only as much evidence for the multiverse as there is for String Theory. Which so far says ... nada. String theorists and Inflation cosmologists (immediately post-Big Bang) and Dark Energy/Dark Matter theorists are grasping at straws, so are trying to ditch the Scientific Method to explain the failure of their current ideas. Maybe nature says ... it doesn't care if ape-men can understand this or not.
