Bitcoin is the king of all digital currency, it price movement always have an impact on other currency,Although for project that is viable and with a product in the real world, there value is not fully dependent on bitcoin price but the roadmap of the project and also news related to cryptocurrency at large, Ultimately Bitcoin will always drive the market trend.
Actually, its not all the time the whole market follow bitcoins movement but yep almost all time the price of all other coins depend on bitcoin closely. Probably Bitcoin is considered as the prelude of cryptocurrency, also its such a fundamental coin that is followed by many people. Plus, most of people in crypto community both believe in btc more than other coins. Generally bitcoin looks like a leader and then the rest of coins base on it.