The NEW ATH for bitcoin really amazed new investors, thus making them to decide to try new kind of asset as bitcoin. There are so many great things happened this year, many altcoins really pump well, just like doge, eth, xrp, trx and other defi coins like uni and cake.
Also, isnt the TESLA who made big btc investments did a loud noise in crypto industry? Other companies envy TESLA making them to reconsider investing cryptocurrency, too.
Other companies don't need to envy Tesla. Everybody, company or individual, rich or poor, can buy Bitcoin anytime. The big difference between Tesla and other companies is that Tesla is updated with what's new and actually has the guts to get into it regardless of whether it is acceptable to the conventional investors' world or not.
On the another note, be careful in saying that many altcoins really pumped well. Many of them are actually not. Their prices are rising simply because Bitcoin's price is rising. But if you are looking at their BTC value and not their USD value, which should be what is done, you'd see that they are still actually in red compared to their previous ATHs.
Coingecko, for example, has it that ETH is still -75.9% from its 2017 ATH, TRX -83.0% from its 2018 ATH, XRP -94.7% from its 2018 ATH, and so on.