Classic Why did Deathwing die ?

My question might sound stupid but let me explain.His goal was to escape into the Maelstrom/Deepholm to cause the "final cataclysm". But when we catch up to him we just kill him.Why didn't he escape ? Hell, he even comes out of the Maelstrom when the fight starts. via /r/wow https://ift.tt/3bLN4J8