Regardless of his business successes, Donald Trump has spent decades building his brand as a celebrity.
Other celebrities that have gotten involved in politics:
Shirley Temple
Sonny Bono
Ronald Reagan
Al Franken
Ben Jones
Fred Grady
Clint Eastwood
Donald Trump
Most listed are, or were, members of AFTRA, just like Rush Limbaugh (former sports reporter/announcer) and all the "reporters", anchors, and commentators on the network news.
These are just a small list of those that have actually run for office. Most succeeded in winning their office.
They not only have the same right to their opinion, they can even get the platform to speak it