Of course they did, bcs they see that the price of BTC is more stable and every day is more higher than the previous day. Nobody won't to risk his money, and they know that btc is more credible than the other alts.
You forgot to mention that 90% of the alts died after a couple of years lol.
It very fun to watch historical snapshots on coinmarketcap.
So many alts dead, so many souls lost. So many players rekt and destroyed for ever.