I love how this confirms that Mario is actually a transphysical creature capable of possession as long as his artifact of identity, his hat, is worn by a sentient being.
It’s why he takes more damage in 64 when he loses the hat, the body lost connection with the host and is slowly decaying
The monkey in 64 knew this: He was actually an agent of chaos intent on robbing Mario of the source of his strength, a long-term plan intent on making his body decay, having grown dependent on the sustenance that the parasite (Mario) provided to it.
Who does this monkey work for? Is there a looming threat bigger than Bowser? This, and more, in Mario Odyssey.