He did have Derrick Henry, though.
I think his dismissal ultimately came down to a rift between him and everyone upstairs. Vrabel is not one for bullshit. His last two seasons there were also losing seasons. He's the guy everyone wants, and it would appear that New England is going to yet again hire another former player to be their head coach. Although this one comes with some coaching experience.
As for New England, they got it wrong and were willing to admit it, sure. They're not starting over yet again and now one has to wonder what to make of Mayo's career trajectory. He played for the franchise for all that time, coached there, got hired as an HC and was fired after one year. He's 38 years old and his entire adult professional life has seen him employed by the New England Patriots in some way.