1. Draco Malfoy disarmed Dumbledore: In the battle at the Astronomy Tower, Draco Malfoy disarmed Dumbledore, unknowingly becoming the wand's new master.
2. Harry disarmed Draco: Later, when Draco was about to kill Dumbledore, Harry intervened and disarmed Draco. As Harry had disarmed the current master of the Elder Wand, it became his, albeit unknowingly.
3. Snape killing Dumbledore: This act also contributes to the ownership of the Elder Wand, as the wand ultimately follows the master who has defeated the previous master. However, this was not the main factor in Harry becoming the owner.
4. Harry's belief: In the final battle, Harry realized that the Elder Wand was his, but he chose not to wield it. Instead, he used his own wand, realizing that the Elder Wand's power came from its allegiance to its master, not from its own inherent power.
5. Harry disarming Voldemort: During the final battle, Harry disarmed Voldemort, thereby becoming the undisputed master of the Elder Wand. However, Harry immediately broke the wand, rendering it useless.
Essentially, the Elder Wand's power resided in its allegiance to the wizard who had defeated its previous master. While Draco briefly held it, Harry effectively became the true master by disarming Draco. The wand's power, however, was ultimately not dependent on Harry's usage, as he chose not to use it, demonstrating that true power comes from within oneself, not from external objects.