I completely agree. The difference is the Heat have a very good development system, as opposed to other franchises (Sacramento, Orlando, Washington, Minnesota, etc.) that do not have good development systems. For Marcus to land with a team like the Heat, he could improve. With some of those other teams, that is less likely, meaning he would be unlikely to ever make it to the NBA, with that team or any other.
Mahomes isn’t the only QB to dip his toe in the MLS waters. A couple of years ago Russell Wilson became a minority owner of the Seattle Sounders. Both teams vying for first place in the conference.
In the NBA, James Harden, Kevin Durant and Steve Nash all own part of other MLS teams. And LeBron bought into Liverpool FC.