It has already killed them. Collective human greed by bad and good people will never lead to a situation where other cryptocurrencies are gone. If you think about it simply all those project founders and developers who claim to have a mission to improve the world would have contributed to Bitcoin and made it better if that was true. But they are just trying to sell you their greed with lies, and many people fall for it. They are not interested in making anything better, their primary interest lies in lining their pockets. As long as this is true other cryptos will exist.

I think you are very strongly underestimating the count. There are currently millions of dead tokens.