You said it. Some altcoins were survived when BTC downtrend goes on, but it just less than 10% of total altcoins were survived. I don't know why people sell their altcoins to buy BTC when the BTC price goes down. It will be good if they sell their altcoins to FIAT or Stablecoins directly.
the reason may be simple because I think everyone here is interested in actual btc and no one denies it, and when btc is currently experiencing a decline of course this is like a very beautiful discount. it's a different story if they put it into fiat because there our assets will be like that and that's all and of course this is not profitable for those who intend to invest