It's also the fact that these movies aren't real (hello !) and can and should be interpreted as metaphors.
The central thesis, the universal unifying theme, of superhero movies is that violence is the best tool to solve problems. All or nearly all superhero movies rely on violent climaxes, with the hero defeating his adversary using punches.
Given that it's fiction, it's necessarily metaphor. Within the real world "heir apparent" don't rely on duels to defend, they might offer the opportunity to debate and to campaign, or to lobby within a ruling class.
That's hard to show on screen in the context of a two hour movie, so it gets distilled as combat. Partly because it's efficient, and also likely partly because it satisfies our own internal blood lust right now. The world is falling apart and many of us instinctively wish that a benevolent strongman (like Black Panther or Iron Man) could come in, beat the **** out of the bad guys, and then fix things. We know that this can't be, so we indulge in this vicariously via superhero movies.
I predict that the greater the level of systemic and unresolvable failure within society, the greater will be the public demand to indulge in superhero narratives. Do recall that Superman started off as a Great Depression comic where he beat up bankers.
Arguing that the succession fights "don't make sense" misses the point entirely as none of the MCU "makes sense" when taken literally. Ray guns, Asgard, infinity stones, etc it's all fiction that is best interpreted as metaphor if one wishes to interpret it at all.
