I like Bitcoin and hope that it will be the one people use when massive adoption comes. But it seems to me that Brian is right that it's a question whether Bitcoin would be able to do that. The number of users is still very low, so a Telegram token or a Facebook one can theoretically overcome Bitcoin's dominance overnight (that is, if we count them as cryptocurrencies, of course). I don't think that a decentralized pseudo-anonymous currency like Bitcoin can beat it in terms of the number of users, but Libra or something really might.
they obviously don't intend on letting that happen again. they know (as well as i do) that altcoins will go crazy again in the next bubble, and they are positioning themselves accordingly. in april 2017, coinbase only had BTC and ETH listed. now they have dozens of shitcoins, something like ~60 markets in all, and more to come i'm sure.
I don't know that. I think that the time of the altcoin market flourishing like it used to be in 2017 is over, and it won't happen again. Unlike the previous time when Bitcoin's dominance was going down (the thing that Coinmarketcap and Coingecko call 'dominance'), it did not decrease when Bitcoin recovered (more or less) throughout 2019. Some coins might rise, but I don't think that most of those even in the top-50 will.