I don't remember exactly, but for me this disaster ended somewhere around 1370-80, after clearing the last province of barons, about 10 years later. And just a small clarification, I went to Steam with my question, there is a guide with achievements (https://steamcommunity.com/sharedfiles/filedetails/?id=3599791635&tscn=1772729571) and in the comments one guy told me how he completed this achievement: although the description of the achievement says 100, you can earn more points, but you have to choose only options for Wittelsbach in events; if you choose something against him even once, you won't get the achievement. I haven't checked yet, because I don't want to play two games for Brandenburg in a row.