Actually Bitcoin price often influence altcoin price but there's a season where altcoin do extremely well even when Bitcoin is stagnant or declining. What if this season comes More often, what will be the faith of Bitcoin?
Yes, Some altcoins perform better when Bitcoin is stagnant since some Bitcoin trader do transfer some of their funds on altcoins trading.
There’s some fundamental that affects altcoin price such as exchange listing, news and other good update regarding the tokens.
There’s majority of altcoins follow Bitcoin trend but some excel due to their community strength to hype the market.