It is called the first mover advantage
But it is not only that, of course. If we cut the crap, the price of all crypto (Bitcoin included) is determined by speculation, and in these circumstances it doesn't really matter how many transactions Bitcoin can actually process daily, hourly, or whatever. What matters is how reliable and secure a coin is, and this is exactly where the first mover advantage comes and shines. Technical metrics like the number of transactions per second and similar stuff are important only as much as they can contribute to hype, not actual application because there is no such application