While it's not ideal, I don't think Minnesota has a problem with Rubio staying overseas two more years - in fact, I personally think it's great for them. He's not NBA ready right now, so he can take two years (when he's still only 19 and 20) to develop in a much better professional league than the NBDL. Minnesota doesn't have to pay him while he's over there so they save cash and hold onto Rubio's rights. And if they don't make any trades, well, they have Jonny Flynn, who's much more NBA ready, stepping in to take the point.
So they get two years of development for Rubio without having to pay him the $5 mil or whatever they'd have to pay under the rookie scale. And when he comes over, he's a 20 year old, more polished, NBA-ready player under their control for up to four years, instead of (if he stayed here those 2 years) probably a less polished (due to less development) player only under their control for only 2 more years. Under the present scenario, he'll be making manageable money when Love becomes due for an extension, so they can stagger money better. And they've got two years of experience for Jonny Flynn, during which time he has ideally driven up his trade value.
So best case scenario, they'll have, in two years, a quality NBA point guard (either one), plus another to include in a trade to fill in other missing parts around what should be a solid frontcourt core (Al and Love, if Corey Brewer comes along) entering/in their primes. Worst case scenario, Rubio and Flynn both flop - but that's the same worst case scenario as if Rubio stays. And the best case scenario if Rubio stays is you have two point guards fighting for playing time only under their control for 2 more years, instead of one for 2 years and one for 4. If the worst case scenarios are the same, I'm happy taking the better best case scenario.
As for the "dumb" trade by Minnesota giving up OJ Mayo - they traded Mayo for Miller and Love. Miller got them Rubio. So they basically just got Ricky Rubio and Kevin Love for OJ Mayo and Randy Foye. I'd take that deal, personally. A real point guard and a very good big man for a very good scorer who dominates the ball but isn't a point guard and a small guy who's at best a third guard.