The crucial decision to not renew the contract enables Saudi Arabia to sell oil and other goods in multiple currencies, including the Chinese RMB, Euros, Yen, and Yuan, instead of exclusively in US dollars. Additionally, the potential use of digital currencies like Bitcoin may also be considered
trump is touting bitcoin because a cryptobro got close to him and or because he wants to grab that cultist libertarian vote
That may be a part of it, but he’s also very tight with the Saudi royals, hence Kushner’s multi-billion dollar deal with them.
You are correct that it appeals to libertarians as well though. It was one of the few times he didn’t get boos when he spoke at their convention.