Yeah I feel u. At least I had a reason to lose. You shouldn't lose with that kind of prep and that kind of team. I would be raging mad had it been me. And 4-0 is kinda over the top. It's tough to fight back like that.
But don't give up. Sometimes after a troll loss, they let you score just enough in the 2nd leg to proceed.
Forgot to ask this but did you sub out the poor performers and adjust your tactics during the match. Sometimes it helps