What makes a player lose their morale so fast?

In rank every assumes the match will be victorious, but when it backfires they start to panic and flame. Why enter a match especially rank and lose your momentum over mistakes? You can't overcome that condition until you try, but then players rather argue on that logic and continue their destructive path. I wish players wouldn't give up so easily sometimes and focus on the victory or try and not who kill steal this and whatever nonsense they like to spew.