Thats one way to look at it, or the other is that changing out staffs on both sides of the ball in the same offseason after the first year would be unprecedented. Bigger issue last year was O. Bigger issue this year was D.
I don't think it's disputed that Diaz planned on firing Rumph as one of his first acts (easy to Google that Diaz was not expected to retain Rumph). My understanding is that Rumph is very popular with former players, and Diaz's preffered replacement went off the market, so he ended up giving him
another year.
This is the lifetime career decision for Diaz. Head Coaching career is over if he sticks with his dudes. He seems like a bright guy that really wants to succeed at Miami. I don't know that he will make the right decision but I'll give him the opportunity to act or not act before making any sweeping pronouncements about whether he's scared to bring in anyone that challenges him.