Why do people get tilted so easily?

Just came out of a game where {{champion:45}} massively overkilled the enemy {{champion:67}} (His Ult dealt like 1.5k fucking damage, Vaynes hp ws around 1.8k), so I type 'RIP lmfao' and this Vayne just goes off on me 'report this fucking Darius for flame' and everytime I die or kill her she just continues, 'lol lifeless Darius main' etc. Wtf? I thought it was funny that one Veigar R dealt 85% of your hp, why are you going off on me?
Report as:
Offensive Spam Harassment Incorrect Board