Well... we know (from insight) that it will be better for the monarchy to do this (arresting, trying and executing John and confiscated his lands in the kingdom), however, back time, it will not be so evident. John was pretty much very involved in the French politics. Doing that, you just cut half of the lands of one of your most powerful vassals which now held only lands outside of the kingdom, but in the mean time had a HUGE claim on his lost lands. Not to speak about the possibility to physically size those lands, which was out of the reach of the French government then (it was not for nothing that the Armagnacs and the Bourguignons fight each others... ).
So, if John the Fearless is arrested, executed and had his French lands confiscated... all you have is... not very much seized. Yah, maybe some of the lands will rebel against Philip the Good and declare their allegiance to the French crown... other might be conquered by the royal army (by the way, which royal army?) but nothing so drastic.
Both your examples are happened during the reign of exceptionally powerful kings which could and did exert power over their vassals and could and did seized lands from their vassals. Who will do this now? Charles VI? Charles VII? The Dauphin is nothing yet than a... 4 year old Dauphin...