Agree with you about the nobility of the period. A pretty dishonorable bunch.
The nobles, however, were leaders. Couldn’t accomplish much of anything if large numbers of people chose not to follow.
After Bosworth the nobles appeared to lose their ability to mobilize sufficient popular support to launch effective armed rebellion. Didn’t stop noble intrigues and such, but it moved to another level. Generally competition for the favor of the king rather than competition against him.
Of course there are alternate explanations for the loss of aristocratic independence. My personal favorite is artillery. As long as effective armies consisted largely of mobilizing men, horses and personal weapons, the aristos (if enough of them got together) could go one on one with the King.
When an effective army required efficient artillery, they lost this potential. Artillery cost too much for local lords. And even if you could get the guns and men together, you couldn’t practice with it in secret. And effective artillery requires a lot of practice.
You would probably know more about this than me but I believe Richard the Third owned one of the first “hand guns” in England (I may not have the right term, lol!). He was a big fan of artillary but didn’t like the gun because of its kickback.