If you have been truly familiar with crypto for a few years, then you would have already known why Bitcoin is the most popular among tens of thousands of coins and tokens.
First of all, Bitcoin came first. The rest followed. There is a huge difference between the first and the rest. The movement from zero to one is the most difficult. It's a breakthrough. It's precious. It's incomparable to the movement from one to many.
Also, Bitcoin is what decentralization means. The rest cannot claim the same.