Wrong. Most executions had no trial or just a mock one (very rarely, most of the time it was off to the chop block, see ya, bye!).
He doesn`t. He`s actually spot on with it. Entire lineages of nobles and kings were slaughtered by all sorts of warlords (vikings would be just one of the examples that comes to mind, killed boatload of nobles in England, did that stop them from enforcing their rule on the land for 200 years? Nope.) One more so you can understand how actually of an unlawfull period it was. Famous Robert of Bruce, first independent king of Scotland, kills his rival in a CHURCH! Does anyone care? Nope. Any trials? Nope. Reason for meeting the guy there? Truce and alliance! Loads of barbarian tribes from the east came in Europe and murdered loads of noble lineages from Germany and France for instance, same happened in the former Byzantine Empire, even in Iran and North Africa among muslim cultures. Ottoman empire had loads of sultan heirs killing each other like it`s no tomorrow (as a romanian there`s loads of documents from my country that depict local romanian lords joining one side or the other in these conflicts).
Yes they were. It was Western Europe that came out of the lawlessness first, but lawless were the times nonetheless!
The problem in bannerlord was actually pretty good implemented the first time around. Maybe add the hatred of the executed guy`s clan. Anything else though is just dumb. And seing how lords just magically spawn with an army instantly after being defeated, killing them remains the only option to actually conquer the map if that`s the objective you set for yourself.