It is possible that other altcoins wouldn't also survive if bitcoin will disappear. More like the investors will not trust any transactions in the crypto world if bitcoin just crashes.
Not really that altcoins won't survive if bitcoin disappears. It's just that it would make the whole crypto space boring. Bitcoin is a leader in this field and without it would look like not having the USD in a pair in forex trading. The volatility won't be there for traders to easily and quickly take profit and that won't be nice.