Technically, that's not quite true
Most altcoins (Litecoin, Ethereum, EOS, etc) had also shown quite spectacular performance at first. In fact, they were massively outperforming Bitcoin for some time (e.g. Litecoin rose 7 times from its early 2019 lows). But then the correction started, and while for Bitcoin it was indeed a correction, for the rest of the pack it looked more like a painfully long panic sell (even though the altcoin market is still far from its yearly lows)