IIRC, the official gossip is that Capers wanted to can Palmer at the end of last year but dint. And then after the offense looked so ghastly in the preseason and first two games, he finally pulled the trigger.
Palmer was hard to get rid of because he is a likeable personable guy.
Fangio got more leeway, IMO, because to some extent, our defense in our first three seasons helped give us more wins than we prolly should have had given our talent/depth.
Personally, early in the season I thought that the defense looked so horrible because they were on the field ALL the time. That it doesn't matter what D you have if every offensive possession is 3 and out.
But over the course of the season, it became evident that the Pbuc experiment was non-good and that we were too inexperienced on D. By the time it was clear that the bad D was the biggest difference between this year and previous years, firing Fangio became kind of pointless because the season was already crap. And to be fair, we have had a ton of injuries on defense--it is hard to keep it together when most of your secondary is comprised of last week's practice squad, rookies, and ST guys.
I actually was encouraged by our run defense this last game. It didn't look like the stick of soft butter defense. And we had some sacks. Just not on the last play.
Anyhow, I don't think it was some conspiracy to keep heir apparents away. I never thought the Capers/Palmer marriage was a good thing. And IIRC, someone tried to hire away Pendry during the off-season and we said no interview. I think Pendry as OC was something that they had been thinking about for a while and was just waiting for Palmer to tie his own rope some more.
Or maybe not.