I think your assuming Bitcoin is bigger than it actually is and the technology is flawed for mass adoption.

If by some miracle we achieved mass adoption, for the first two to three years, most transactions will be small low valued transactions until the masses learn to trust this new digital money. Unfortunately, you can't do small transactions with Bitcoin and the masses won't accept paying an equally large fee. THIS IS A MASSIVE PROBLEM that will stop mass adoption because if this is peoples first experience of Bitcoin, they will dump it and forget about it.
Bitcoin is desperately trying to get the lightning network used to solve this problem but not even their own community or maximalists are using it because it takes away the direct P2P 'permissionless' appeal of Bitcoin.

Personally, I hate to say it because I hate the idea of it but I think Ripple XRP has the biggest chance of global adoption simply due to the work they are doing with the IMF and attempting to disrupt SWIFT. The Ripple community are currently waiting for the big announcement that will give Ripple a government approved global currency status. I hate the fact that Ripple is working with governments and the global establishment but by doing this they have the best chance of global adoption as things stand today.

Also, before this contentious hard fork of Bitcoin Cash tomorrow, I would have said that Bitcoin Cash had a much better chance of mass adoption than Bitcoin simply because it can process small transactions and because Bitcoin.com is only promoting Bitcoin Cash. The masses are generally stupid and most people will visit bitcoin.com and think Bitcoin Cash is the real Bitcoin.

So to sum up, Bitcoin is in a lot of trouble in regards to adoption and I don't believe they will be the first anymore. You only have to look into the community and read all the fighting going on and the negative image that all of the maximalists are creating around crypto.