Polkadot has risen around 172% since October 2023 while btc has risen around 127% at the same time. So what are you talking about?
Are you asking why it crashed so hard after ATH? There are ton of reasons for that, but main one would be that DOT wasn't anything special. It shouldn't have any reason to get to new ath, but since markets are dumb, it's probably going to do that as well at some point. But i personally don't want that crap to my bags. Even meme tokens bring more value to crypto.

And since biggest security issue in crypto for a while has been cross-chain bridge vulnerabilities, why would people want to invest to a coin, that's basically build around that subject?