Slop.

It kinda goes hand-in-hand with having a harem of objectified and dehumanized subordinates that Isekai is founded upon, it's just a natural development from the premise itself (unmitigated misogynist fantasizing that appeals to teenage boys in a reactionary imperialist/colonizing culture)

Isekai, at its core, the appeal is "what if I could go to this unspoiled mystical land and be superior to everyone there in some way and dominate them?" It's the colonial urge. It's not a coincidence that Isekai MCs are always godlike OP for no reason whatsoever, so that they can exert their will upon the "NPCs". And since the MC is a stand-in for the audience, what they would almost always do is create a harem of girls - the more helpless and dependent the better - that they have total power over. (Over-compensating for their past incel life where they could never get any girls)

You have the two flavors generally. The more normie-coded benevolent Isekai dictator, who merely happens to accumulate a harem of girl followers through his good deeds & the incel-coded evil Isekai dictator, who lecherously indulges in what he's doing. Some anime fans would like to say only the latter is reactionary, but really they both are. The first one is just the "rightful king" and "white/japanese savior" and "white mans burden" all combined (the Japanese see themselves as whites).