If you ever feel useless

They're not his bodyguards. They're there to hold him back as long as they can while you run away. This is not to give you an chance to escape, but because he gets disappointed and sad if the hunt is over too soon.

The difference is that the short man in the suit has professional liability insurance.

If someone tries some dumb shit and gets a pavement facial Moama can almost certainly beat an assault charge, but civil injury claims are notoriously bad if you're rich. An ambulance chaser will offer to take the case for free and be such a pest that its worth $100k to Moama to make him fuck off.

The little guy can sit there in court, dispassionately explaining that he felt his client was in danger and let the ambulance chaser argue with an insurance company (and we all know how much they love cutting cheques).

So you’re saying their job is to protect Mamoa from the law and others from him.
- Also sure, Mamoa is a big guy and fit, but he's an actor, right? Not a fighter?
  
  It's kind of like how Nick Offerman said in an interview once. Everyone sees him as this manly man because of the roles he plays and because he wood-works. But he's from a real "country" family. A rural farming community where everyone was self-sufficient and real "manly" men type. He's the one who wanted to be an actor who never has to work with his hands again.
  
  What I'm saying is those men have jobs where they protect people from physical violence with physical violence. Jason Mamoa pretends to hit people on camera.
- No.
  
  If a crazy fan rushes him for a hug, you dont know if they have a knife. It sounds outlandish but Monica Seles was stabbed by a deranged fan of her rival in 1992 in the middle of a tennis match. Nutcases happen. So he pushes them away, no harder than you or I would if some rando rushes us for a hug. They trip, fall and "hurt their back".
  
  Now he has an assault allegation on a woman a foot and a half shorter than him who just wanted to get a photo with him and he looks like an enormous asshole. Now that charge wont go anywhere in court because its essentially baseless, but a civil judgement over wether or not he is responsible for her injury is another story.
Can't Mamoa just get a regular liability insurance for such cases?
- Probably, but why? For the same price he can someone else deal with all the bullshit.
  
  Part of being rich is not dealing with all the bullshit.

Another fun way I've seen this pic captioned is, "Jason Momoa's bodyguards look like minibosses you have to fight before you get to him."

Haha they do indeed 😂

Yeah, because size, looks and macho roles you've played suddenly count as fighting skills....

Momoa does Brazilian jiu-jitsu though.
- He's a white belt, so still very much at the beginner phase. He'll also almost definitely be one of those celebs that only does privates and rarely spars.
  
  He'll almost definitely have strength and size at his disposal, but in terms of fighting, we've already kinda established what would happen at UFC 1. A skilled bodyguard would (I really hope) have solid grappling knowledge, alongside striking.
- Why would he risk injuries in a real fight when those could damage his career temporarily, though?
Never underestimate your opponent, especially a stranger in the public you've never met before.

I have a friend who is a retired military police officer. He is built like a tank, tall muscular and intimidating.

He's the one who taught me never to underestimate anyone. He man handled, beat and fought countless people. But he also admitted that he'd been beaten bruised and hospitalized by people shorter and weaker than him.

When you fight someone in public, you never know who you're dealing with .... he could be an untrained jerk like you and me .... or they could be a 150 lb MMA fighter and highly trained martial artist with expert training.

Or the person you're fighting could have a knife, a pencil, a screwdriver, a piece of glass or their friend or friends you didn't see or believed wouldn't interfere all jump you and beat you to a pulp.
- You're absolutely right.
  
  For sure the probability of a dandy actor to be match for a psicho, who is preparing since who knows when, for the kill is really high. /s
  
  You know people tend to specialise in a field of activity for a reason. I will go with the punny but we'll trained and conditioned bodyguards over the "imposing tank" who is said to be tough right about... any time!