I don't think Bitcoin was the first coin in the market back then, there's already a lot of existing coins but it would eventually die. When Bitcoin existed, its worth of course started from nothing as we can remember the story of buying a pizza with a huge amount of BTC. Eventually, after a long period of time, Bitcoin has proven its worth by not only surviving for years but also by gradually increasing its value, that's why it gained a lot of attention from investors so it's widely known and used cryptocurrency. Bitcoin is the king that causes the existence of other coins as well and they took inspiration from the creation of Bitcoin. As Bitcoin increases its value or decreases, it affects most of the movement of the coins in the market.