On January 2010 on Minecraft version v.1.1.2_01, a player named sf17k decided to try his luck and speedrun for diamonds. This was the first ever “speedrun” attempt in Minecraft history. This point is believed to be the start point of speedruns people know now.
In 2011 people started getting more advanced in their speedrunning. For example here’s a person speedrunning a nether enter for the first time ever. But the start of real speedrunning begins as Minecraft officially releases on November 18th 2011, adding an Ender Dragon and changing trajectory of speedrunning forever.