Or is it that the Knight faction starts with 100+ Knights, and that's not the reason? Let's avoid these "what ifs" and look at what actually exists. I see a Knight faction that, if played by someone with a decent skill level, will crush any bot, regardless of difficulty.
And if you add mass haste + the ring of swiftness, as well as the staff, the scales will tip in your favor. And Darkness is also quite easily countered by Light, even with the Knights.
Okay, let's say I build up legions of an army, would machines still be relevant? What about Chaos, summoning?
...the ability to play Heroes includes the ability to properly develop a hero depending on the type of map. Some skills are beneficial on small maps, others on large maps, and so on. If this weren't the case, the same universal hero build would always be used, and then the question would arise - "why are other skills even needed if this universal build is the best?", so let's just throw out half of the skill wheel...
I also want to correct you that the development depends not only on the map, but also on the opponent.
Блистает там воздушностью прогалин.
Но между кедров, полных тишиной,
Расщелина по склону ниспадала.
О, никогда под бледною луной
Так пышен не был тот уют лесной...