You give them too much credit on this one. This decision was likely spearheaded by some nepo appointment who is out to diversify in the worst way. When your send cousin Johnny to college in the West, you're still not getting the best and brightest when he comes back. Whole structure of their investment fund is graft and bad decisions.

Compare Saudis system to Norway's sovereign fund. Instead of being politically neutral, like everything in the house of Saud it's a patronage system. They do big headline buys like this to convince everybody above them they're actually doing something to diversify from oil market shocks. But in this case they're buying a dry well that's already had it's data sold to those who wanted it and is burdened to IP licensing that likely drains much of its micro transaction potential while also being able to be revoked if the parent company stops liking what they're doing. They're not going to get much from a state security standpoint from it that they couldn't get in ways that would cost several billion less and they're not going to get much of a return of investment on it either. But since patronage rewards are front loaded they do stupid buys like this.

If they just wanted the data, they could've gotten it for much less than 3.8 billion. They likely could've gotten it for 3.7 billion less at least. Or just send some guys to steal it like they did with Twitter back in the day. Much cheaper.