Honestly, Viserys wanted it. He made the decision after it became clear that he would not have a son with Emma that survives to adulthood, and maintained this decision even though he had three sons with Alicent later on. Rhaenyra did not have much say in the matter at least initially, she was not asked.

I disagree with you about her not wanting the crown later on. I mean, if she truly does not want it, then why does she not accept Aegon II's terms? Those were not unreasonable, she was allowed to keep everything that she already possessed + Dragonstone was gifted to her even though it belongs to the crown prince technically. There is also no reason for "revenge" if she truly does not want it. Daemon was the one pushing for war for IMHO no good reason, there is no reason to believe that Otto, Alicent, Aegon II or anyone else goes after them if they publicly agree to settle for Driftmark and Dragonstone only, that is, as long as Daemon behaves and does not stir up rebellion. Daemon the warmonger won over the better judgement of Rhaenyra, however she ultimately agrees with him because she does in fact want it.