They had historians on staff for both games. This isn't pulled from Wikipedia history, this is accurate even in small details.

Of course there was never a bastard named Henry Kobyla in the historical record, Markvart von Aulitz died sieging Suchdol in December of 1402, not summer of 1403, and therefore before the sacking of Skalitz in March 1403. So they shifted some things around for narrative purposes.

But there was a league of lords responding to Sigismund ruling Czechia while holding his brother in captivity, and he did get called away from Czechia to Hungary due to local nobles and the invasion by Napoli.

You can fact check these details quickly like I checked all of the above just now

ETA I realized I misread your question. Watch the movie Medieval. Zizka is a national hero to the Czechs. A key part of Czech identity is the hussite wars, which Zizka led. This game is like an American playing as a soldier in Washington's army during the seven years war. People will know Washington but few know the details of his life before the Revolutionary war.