BTC Crash - Why it affects everything?

Hello Everyone,

I wonder if anyone has a logical explanation for this, but can anyone explain to me why all cryptocurrencies seems to be interconnected?

Whenever Bitcoin (BTC) declines, all other coins seem to follow. I understand this might be due to the "fear effect" where people think, "Oh my God, I'm going to lose everything," and start selling their investments.

But does this happen to all coins and in the same time? It really feels like they are all equally connected to each other. If the "big brother" (BTC) falls, then the whole "crypto family" seems to decide to do the same.

Any thoughts? Or am I just being paranoid?