Both of these firings are lessons in what happens when you fire a coach for underperformance.
Yeah, it feels good in the moment. "I'll show you you're not all that. Get your sorry carcass outta here, loser. You're not going to run down our program anymore!"
The you sit around feeling all good and self-satisfied.....until you realize that now you have to go out and get a new HC. From somewhere.
And if your AD is the one who hired the coach you just fired (and that's the case for both VT and UCLA), you now have a winged AD on your hands. One who now has to go out and convince somebody to be the next HC. When candidates will wonder who their boss will be.
I'm not saying never fire or advocate for the firing of your coach. Sometimes it's necessary. I'm saying don't do it in a knee-jerk reaction to a disappointing game or season.
Hiring a new coach is always something of a crapshoot. You just never know how the new guy will work out. Many forget that while Saban was the closest thing to a sure thing, there were doubters due to his reputation as a money-grubbing job-hopper, the fact that very few (none?) of his assistants followed him from MSU to LSU, and the fact that he wasn't all that successful in the NFL.
You need to ask the question, "Who would realistically come, and most likely would represent an upgrade from what we have now?" I say most likely because you never know for sure.