In the first instance, a crash isn't like being dropped on the descent (which undoubtedly in the overall economy of the course, would have been SK's best option and probably would have saved him the title). He didn't "have to go down", because of Nibali's pace, but "choose to go down" trying to follow. If Nibali had just dropped SK and then went on to still win, then it could be said he did so entirely on his own legs. As it stands his victory was helped by Lady Luck. "Luck" as the opportunity he created, true, but it still doesn't show the real strength or weakness of the players in contention. One was simply physically compromised and the winner who capitalizes on his rival's impairment, with however much bravura, isn't the same winner as if he had dominated a healthy opponent.
Let's remember that Kruijswijk was 4:43 ahead of Nibali before the crash. Consequently anyone that denies that the Dutchman was the strongest in the mountains till that point, simply negates an unequivocal reality. He dropped Nibali on the queen stage in the dolomites, finishing with the stage winner Chaves. He dominated both Chaves and even more so Nibali in the MTT. He was never dropped by anyone else on a previous mountain stage. He was ahead of Chavez by over 2 minutes and by Nibali and Valverde by over 4 minutes. It is impossible to state he wasn't the dominant rider up till that point.
Practically the only thing that could have unseated him was a crash, which is what happened. So Nibali was very lucky. Without the crash the Giro probably wouldn't have been his.
Now in regards to "only the Tour" blah, blah, blah, blah. Hey I've lived in Italy for over 20 years, so you've picked the wrong target for such an accusation. To the contrary the Giro is to be appreciated for its own merits, independent of the status of the Tour, which is though undeniably the biggest race on the calendar. That's why I said none of this debate matters come July, for the simple reason that at the Tour every contender departs from a tabula rasa. If a guy wins the Giro but looses the Tour, everybody is talking about the guy who won the Tour. If a guy doesn't ride the Giro (or looses it as has happened), but wins the Tour, everyone is talking about the guy who won the Tour. Not surprisingly all the best GT racers in the world are there to fight for cycling's biggest crown. As beautiful as the Giro is, this isn't the case with the Italian GT.
And nobody said Nibali was "weak," or that winning the Giro isn't a huge achievment. I don't know where you gathered I was inferring that from. I find the Giro parcours and general interpretation of how they are raced to be far superior to those of the Tour. The Giro is still primarily about cycling, whereas the Tour is about the prestige and colossal enterpise of the race (with the obvious significance this has for the cyclist who wins it). If anything consequently mine shows real respect for the dignity of the Giro and its place in cycling, in simply poining out it's a shame that the winner's outcome was greatly enhanced by the crash of the guy that had dominated him and the race till that point.
Otherwise if all we care about is that Nibali won the Giro and not how he won it, then we might as well have rooted for SK to go down while in such a commanding lead.