The true origin of the gaming term "cracked" had its origins from the game Apex Legends. In Apex, when you break an opponent's shield, an audible cracking noise occurs, indicating the opponent has about 100 health remaining. When Apex players would cross over to play Fortnite and play random squads, they would often shout during heated mid-game fights "He's cracked!" to indicted to teammates that the enemy has no shields, just like in Apex. The Fortnite players who did not play Apex, and were unfamiliar with the term, thought the player making the expression was giving a heat-of-the-moment complement that the opponent was very good. As time went on, more Fortnite players would start using the term "cracked" in this misunderstood context.
Player A: "He's cracked!!!"
Player B: "Yeah, that guy's pretty good."
Player A: "No, I cracked his shields!!! Don't any of you guys play Apex???"
Player B: "Sorry, all I play is Fortnite."