Make minecraft use all your pc cores / threads instead of only one

Using one single core for the past 15 years...
Multi-core minecraft would run x1000 times smoothly, the slow chunk loading will be gone for almost everyone, an insane amount of tnt exploding will lag ur pc, but atleast not crash the game.

Multi-core Minecraft has many benefits, but i know re-writing the code will take forever, so mojang could work on it as a 2nd task, and focus in the drops and updates