Cybersqatters, simply put.
Marriot will eventually pay for it, considering the search driven internet we live in.
After too many users keep accessing the wrong site, and they complain to Marriot about google searches leading them there, Marriott will react.
More users going to the wrong site drives up its traffic and thus its Google search ranking, leading to yet more users going to that wrong site.
Eventually, Bonvoy searches would lead directly to bonvoy.com...
It is how the internet works.
Any marketing/branding/advertisement professional worth their salt would see why Marriott not owning the .com domain is an issue that hurts the company. Lets see how long it will take to get here.