Billy Beane runs another American baseball club, the Oakland Athletics, not Boston.
This group he has put together would be buying into FSG, not Liverpool per se. Reportedly there is an idea of building a network of clubs similar to what Red Bull has done, where Liverpool would of course be the pinnacle similar to the way RB Leipzig is for that outfit. The idea of course is teams where players from all over the world can be signed and developed before being sold or moved to Liverpool.
FSG have always said they are open to a major investor.
As far as Moneyball being buy low and sell high, remember that in American sports, players are not acquired via transfers between clubs. They are either swapped under their existing contracts or purchased as free agents (think Bosman transfers).
But in Beane's case with Oakland, the owner didn't have the funds to compete with bigger market teams like New York, Boston and Los Angeles, so he used analytics to identify players he could sign for lower contracts. It's much more about buying low than it is about selling high.