MicroPython's a bytecode interpreter so, other than the existing Python ecosystem being a huge boon (popularity being a form of strength), you could get many of the same benefits and more from wasm
You can actually opt-in to native compilation on a function level so it's not just a bytecode interpreter. You can also compile it yourself with additional functionality written in C/C++ and just use Python for the glue that isn't performance sensitive.
MicroPython, like most BASIC interpreters in 8 bit days, also allows for inline Assembly.
As for running bytecode on MCU that is as old as MCU themselves, wasm doesn't bring anything to table.
https://en.wikipedia.org/wiki/BASIC_Stamp