Hmm, that's good for you to know about Bitcoin. 
 
You ask that why Bitcoin has become so popular.
The simple fact is that Bitcoin is the world's most trustworthy and largest market cap coin while Altcoin doesn't have that much. Second, Bitcoin was the first public cryptocurrency, while altcoins followed. Is the second Bitcoin the first Altcoin, That is, the foundation of Altcoin was created after Bitcion, so how can Altcoin be better than Bitcoin. And this is considered to be the main reason why Bitcoin was considered popular. 
 
And finally, let's say that Bitcoin is the only coin that has the potential to hedge the world from inflationary fiat currencies along with value surges. So I think this is the point from which Bitcoin is considered so popular and so good compared to Altcoin.