Why such anger and surprise now?

Ozil has to be admired for boycotting the final in support of Mkhitaryan

Not really surprised as it’s happened toward the end of this season, and countless times under wenger. Still shocking to see though and hard to comprehend. We were defending pretty well, getting in behind, dealing ok with hazard and in a good position for second half. Something goes wrong, then on the pitch it’s 1 2 3 śhït yourselves! In once instance an entire game plan forgotten about and the players all collapse. It’s an age old story. Emery seemed to fix it at start of season, as we had good amount of fight back. But it soon ebbed away. There as usual is no leadership on the pitch, no one to re focus the player. 80% of the time the players response to going behind under pressure is to totally give up. That will largely remain the same until basically about everyone but 3/4 from last night are replaced

you have no leadership on the pitch. In the past the Arsenal captain was always a strong character like Adams or Viera who'd get you through a tricky situation.
I genuinely have no idea who your captain is now, and I don't see any leaders on the pitch.
You're a decent team when things are going well, but you've too many players who, if you're winning 3-0 will make if 4, but will go missing if you're losing.

I'm not sure we really fixed it at the beginning of the season tbh, we got very lucky results wise on that unbeaten run.

Overrall there was a slight improvement this season but we're still so far off being at the required level I fear it'll take at least 5 years of solid management (due to financial issues) before we can even think about competing at the top.