Recently, the price of Bitcoin and other cryptocurrencies have appreciated significantly. This is largely driven by the long term affect of Bitcoin halving.
Most crypto assets including Ethereum depend to some extent, on Bitcoin. When Bitcoin price goes up very high in a short period of time, people tend to sell some of their Bitcoin and buy altcoins.
This leads to a significant surge in the altcoin market. There may be a few altcoins that go up because of other reasons but in general, the main reason is Bitcoin.
This Bitcoin peg is both a blessing and a curse. If Bitcoin succeeds, other coins automatically have a higher change of success but if Bitcoin fails, say a critical bug destroys the value of Bitcoin, all other coins will be affected.