Hi,
I may be wrong but I think that even if bitcoin becomes worthless, it won't cause the death of other cryptos.
Of course, it depends quite heavily on the reason of the "death".
But still, there are other cryptos that are quite powerful and have large communities. And I guess that they won't disappear all of a sudden.
Truth is, the bitcoin is the crypto that has made history. It is the one most people (and mass media) know about. It is the one bringing about many concept about the economy and currency alternatives. Still, even if I believe in it, I must say it is not everything.

If they have powerful and large communities why are all the alts dropping even worse than
BTC ?
Care to explain this mistery?
Bitcoin is definitely becoming a lesser-dominant cryptocurrency, especially when so many are being developed and started as we speak. You've got high and slow transaction fees, high competition to Bitcoin and a growing investor interest in these altcoins.
Same as the above.
If those new developed alts are so good, why are they falling down like drunk ducks?