This last post makes me think you are getting to the heart of the problem, at least what I think is the main cause of this collapse.
Everyone seems to be focused on the players shitting themselves or bottling it....but what if the person we should looking at ( and probably the most scared person in the room ) whose obvious mistakes are borne out of fear and affecting us the most is the coach?
I mean not realising when your team is 2-0 ahead (in a game no one thought you would win) that you need to keep the tempo up at all cost and not give back the initiative? ( note this is the same mistake the Southampton coach made today).
Not realising that there is something fundamentally wrong with your defence which you only fixed once a certain youngin from France was brought in this season straight into the starting lineup? Yes you tried to fix it with Holding but his dynamic is not working...why not try pushing White back or the new kid you bought for situations like this?
And Trossard your assist king, the guy who's been the January signing of a lifetime....is there not a way to ensure he's more involved instead of always coming in when we are chasing games?
Apparently after the West Ham game Arteta publicly said something like the players had lost their belief and were afraid and Xhaka (who whether anyone likes it or not is still the unofficial leader of this group) responded by saying he doesn't know what the hell the coach was on about....
Anyone or everyone can shit their pants, but when the leader of a group ( the manager) is doing the same thing but in denial... where the fuck do we go from there?
And like I keep saying, its not really his fault because he's obviously learning on the job.
Dixon just said the same thing in his analysis.