I disagree that it's the simplest explanation. The starting point is the mind, because it's what asks the question. The physical world may or may not exist out

I disagree that it's the simplest explanation. The starting point is the mind, because it's what asks the question. The physical world may or may not exist out there entirely independent of mind phenomena but the physical laws are a mental model in order to understand the world, the physical laws arise out of the interaction between the physical world and the mind. The operating order is like this: there is mind -> mind perceives world -> mind makes mental model that presupposes the perceive world is independent of mind -> mind tries to determine its own origin within that presupposition. If you simplify to the most extreme degree you're not left with "the physical laws", you're left with "there is mind". As such, the burden of proof is on the side of the presupposition that the external world is entirely independent of the mind that perceives it.