For the crypto world it will take just one large country to adopt it as a national currency and the rest will follow.
The next best thing is if a large country makes a huge investment into the crypto world.
Russia is under lots of sanctions from the USA.
Basically like Iran, the USA has locked them out of what is supposed to be the global currency.
Russia has 400+ billion of investment funds available, and it looks like they are about to invest 10b of it into BTC.
A huge game changer, as everybody else will pile in once it happens.
https://cryptodaily.co.uk/2019/01/russia-on-verge-investing-10b-bitcoin