why should doubt the existence of bitcoin, I totally agree with you that bitcoin is the main market for crypto. bitcoin has become a prima donna for highly sought-after investments because apart from leaving out all altcoin is affected by the movement of bitcoin. There is no altcoin that can control without the encouragement of bitcoin, so we can be sure that bitcoin is very reliable and suitable to be the main investment. although do not neglect to the top altcoin which is also quite good.
Though being a global currency is still too early. But yes, no doubt, nothing can beat bitcoin up until now. The popularity alone among cryptocurrencies is not questionable. Even noncrypto users is associating bitcoin with crypto but when you talk about other alts, they are clueless.