Aegon II, then, is wearing the crown that originally sat on the head of Aegon I, and Rhaenyra is wearing an entirely different crown. As we see in the season finale, Ser Erryk Cargill arrives on Dragonstone with a crown as part of his cargo. He gives this crown to Rhaenyra, who is immediately crowned queen, setting up a civil war over which leader is legitimate.
Source: https://www.distractify.com/p/rhaenyra-crown-house-of-the-dragon