It’s often a thing in RPG’s, and fantasy in general (especially anime) that the officers are warriors like the soldiers, just +1 for every rank. So your grunts are basically cannon fodder, while your generals are basically armies in themselves. Not just the special heroes (or villains), not just the player characters, but just regular generals.
I have no idea how this became a thing. Maybe it’s from ancient myths, where the leaders (usually princes or kings) were heroes, generally at least a descendant of a god distantly, if not directly. Basically, these guys were already great, so they deserve the power and wealth that comes from being great. And being great and powerful, they are nobility, and naturally have men at their command. I guess that would make sense.

Especially when you consider that the officers in the old armies tended to be the nobility. In the feudal systems (which most fantasy is based on), the bulk of men for armies would be provided by the various smaller-scale rulers, as armies are expensive, and food needs to be grown. Even as full-time armies became more common, military leadership continued to be a thing for the rich, especially for non-inheriting sons: education to become an officer is expensive, and sometimes spots were explicitly paid for.
But while those officers might have been nobility, they weren’t more proficient at actually fighting, generally. Knights might have been, but again, they had the money to train, and to get special equipment. And a knight wasn’t necessarily a general, or even a high-level officer.
So we have these generals in fantasy (and sometimes sci-fi) that are supposedly great at fighting. Not just great, but often super-human. And of course they are going out to the front, if they even have an army at all, to be the boss after a bunch of mooks.
But that’s not what generals do. That isn’t what all but the lowest-ranked officers do. Generals stay back, and plan. They lead. They command. None of those things require the generals actually to be up in the thick of things, and indeed are actually counterproductive to their jobs. Sure, the general needs to be close enough to see what is going on, but too close, and that vision becomes both too narrow and too unclear.
If these powerhouses are going to be officers (because mooks always follow a strong leader), they should be low-level, like a Lieutenant or a Captain maybe. These are officers that would be up at the front, doing the fighting. It would also give them a significant amount of authority, in the immediate area.
But such a low rank just wouldn’t do for a significant adversary for Our Heroes, now would it? The villain should be someone Important. And therefore they need an important rank. General would do. I almost think that these characters are powerhouses just so that, when the heroes defeat them, the battle is effectively over: without a general, the evil army just retreats.
Even when the general (or ruler) is in the rear where they’re supposed to be, they’re still a boss. Often one of the last bosses. It’s like, Our Heroes fought all this way, through waves and waves of mooks (or went around them), and now they face the real challenge. But why would you hold such an effective warrior back? I can see holding resources back, only spending them as needed, but as soon as the mooks were getting beat, the strong people should have been sent straight out.
The thing that set me off today was the most recent Granblue Fantasy event. The girl at the top (Shura) isn’t even really an officer, she’s a tactician. A brainiac, not supposed to fight. Yet she’s right there with Dancho (who, ironically in this case, is a strong fighter that isn’t in a leadership role in the army) fighting the big boss at the end – said big boss who cuts down mooks like they weren’t even there, who can literally dodge bullets (oh, and he’s also an enemy general). But she’s not the only one – every general in the story is a great fighter, such that the mooks all stand around and watch them fight each other. The rulers, same deal (the young king on the Good Side, and the young prince on the Bad Side). Even Shura’s little sister, who isn’t special in any way besides being the big bad’s girlfriend (a fact the story points out several times) is still leading a decent-sized force.
But obviously not just Granblue Fantasy. Just out of games I’ve played recently, Dragalia Lost does this. Fire Emblem is basically this idea: the game (though to be a little fair, many of them are Heroes in the Greek sense – but not anywhere close to most of them). It’s a thing in ESO. Heck, you could name most any JRPG. Even in STO, the player character is Grand Admiral Awesomepants Death Machine.