I believe that they're popular mainly because well it was the first of all cryptocurrencies to be made. Honestly most of the other coins are scams and greedy ways that the developers make money. The only other coin I can think of that isn't a scam are dogecoins! What do you think?
Yes, bitcoin is the most powerful and most popular crypto coin. The strong bitcoin makes people believe in bitcoin, and entrust their money to invest in bitcoin.
Actually, the cost of bitcoin is supported by elementary human greed. Man has always sought to do nothing, but to make easy money. I think Bitcoin has grown in price is due to the thirst for easy money.