We are struck down by a long term mentality disorder, but this usually prevents us from achieving things and causes us to fall at the last hurdle so that isn't a problem here as this season we fell on the first hurdle.
It has to be management choices for me.
Martinez started our decline. After a tremendous first season it looked as if we had finally arrived at the top table but in his second and third seasons he was exposed as an incompetent buffoon who couldn't organise a defence that Moyes hadn't already set up and he filled out our squad with some of the worst players I've ever seen. Not to mention the fact he was the biggest BS merchant around when it came to glossing over his own failures.
Koeman was a strange one. Inside a 3 month spell just after Christmas we were ace (at least at home). It had been a long time since we experienced the feeling going into every home game that we were going to batter whoever we were playing. It looked like the balance of the squad was nearly fixed as well. However the team soon fell away again post Coleman injury (which we are still suffering badly from) and after a dreadful transfer window, epitomised by selling our only (fringe) world class talent (and not replacing him) he could never ever get the side going. He had no idea at all how to arrest our slide and in the end he was picking teams that he was hoping would click - the club had no choice but to fire him. I don't think he was fully responsible for the failures of the summer window, in fact I think he's been made into a bit of a fall guy.
As for Allardyce, deary me. He is pragmatic (which I like) but utterly dour, and the team can barely string 2 passes together and the amount of times we struggle to even register basic shots on target points to a deeper issue concerning a lack of understanding on how to set up an attacking team. He needs to get a grip, and soon, to stop us getting pulled back into the relegation dogfight. His contract simply must be terminated in the summer - he inspires no confidence from supporters at all.
I'd like to see someone like Paulo Fonseca given a go. We need a younger, hungrier and tactically savvier operator than we've had with these last 3 permanent managers. Fonseca looks like he plays the game in the right way and unlike Martinez he seems to appreciate that the defensive side of the game is just as important.