Bitcoin is a unique asset in the crypto world. He was the first, went through tough tests (attacks, prohibitions, skepticism) and proved his resilience. Altcoins, including Ethereum, are developing in an already prepared environment, where bitcoin has taken the brunt of the blows.
Ethereum and other altos are solving their problems (DeFi, smart contracts, etc.), but bitcoin remains digital gold - the most reliable and recognized asset. Its value lies in decentralization, limited emissions, and the trust it has earned over the years. Even if Ethereum or other coins grow, they will not replace bitcoin, but will exist in parallel.
So the collapse of bitcoin due to alts is unlikely. He has already passed the point of no return.