If I'm right in thinking, are these the ones where you pick characters, each with different weapons and go into fps environments and battle? It's very different from a fighting game, before everyone suddenly starts thinking about that. Instead of going one on one you sometimes go two on two, or even six on six, or maybe even larger. Also, the abilities are different too. So some characters might be able to heal others, some might be able to cause stuff to happen although I can't really think of any examples.
Unless Overwatch is one. I don't really play it as it's not really doable but there's a character called Tracer who can, I think, leap great distances or something, there's a character called soldier 76 who has an ultimate ability that basically auto-aims, there are characters who can use melee and there are characters who might be snipers but two sniper characters play ver differently from each other.

A decent MOBA would not be hard to create, given the resources we have already... the problem is that there aren't enough developers in our community who put enough time and are knowledgeable about the way combat works to actually make a game that's complex enough to keep people coming back. Every example we have of an FPS is a point and shoot type game where mashing of the fire key and who can press the arrow keys to aim the fastest is way more advantageous than trying to come up with any sort of tactic or play smart. That's not a bash against any particular game or people, just a statement of fact. As Dark Said, we don't even have a fully functional Zelda Style RPG with attacks based on timing, not in English, anyway, since we are keeping Japanese games out of this discussion. But communicating multiplayer combat in a an arena without decent audio cues rather than an overwhelming meriad of beeps and tones is very easily doable, both if you know what combat, especially combat in video games, is like, and if you can picture combat tactics and strategies. As Dark said, once you add in the factor of multiple combatants, the mechanics actually are very similar to a fighting game, so not as different as some may think.