BTC has not peaked by any means. Its rise has been mild so far and it should go near $100K at least. Alts outperforming BTC is a great sign for the best phase of the crypto bull market.
At present many of them I know are more interested in altcoins and looking to accumulate as much a possible. Some getting converted their btc to altcoins, might be just want to catch the trained as seems to be season and altcoins rising very quickly so making some quick profits and may convert back again to btc later on.
I'm sure they feel that bitcoin is already very expensive nowadays, the right choice to look for profit in altcoins. Because the altseason is about to begin. I don't know when, some predictions still don't have an accurate way to go about the alt season. But I'm sure it will definitely happen. It's a good time when bitcoin is high and coins are down to become a collection of coins.