Bitcoin has highest level of trust to investors and supporters because it's the mother of all cryptocurrencies wherein has already cement the foundation for how many now and it proved that it can survive the market dip and FUD from people hating it. Many famous people already jumped on bitcoin and by that alone it added more trust of bitcoin hence it's the future of payment system.
Bitcoin is very popular because it became the first crypto, bitcoin continues to have support from many companies and now we can see bitcoin on many stock exchanges and futures of the world, I believe bitcoin will be more and more popular and become the standard of payment accepted by the world like gold.