Oh it really isn't.
Spoilers: So, TL;DR Wenceslaus cut a deal with Sigismund that would put Sigismund in de facto control of the HRE, leaving Wenceslaus free to drink and fuck as much as he pleased. He then backed out of that agreement since it left him completely powerless and dependent, and began telling everyone Sigismund was trying to take his rightful title from him. Naturally Sigismund got offended at that, and then decided to take power for himself since his half-brother was being an ungrateful cunt. So yeah, because two siblings couldn't get along, a massive chunk of Bohemia got burned to the ground.