Altcoins especially the low market cap ones tend to move faster than those altcoins at the top as they are easier to be pumped and dumped by the whales. People don't want to be bored and investing in Bitcoin might be boring for some as it moves slower than altcoin thus, they preferring to invest into altcoins than Bitcoin as their price move faster. Higher risk = higher rewards.
We've seen many altcoins that just went up and now at the top out of nowhere. Coins like Polkadot, ICP, Solana etc. Altcoins are way riskier than Bitcoin, but can give you higher profits than Bitcoin and that's the reason why people are always interested in investing into altcoins. Profitability.