When I started writing my dissertation long ago in a galaxy far away (early 1990s San Diego), I had a problem: each day there seemed to be a new secessionist crisis, which meant re-writing the intro chapter every day. I eventually learned a key pro-tip: write a very drafty intro and then leave it behind and then re-write it LAST since the diss/article/book will inevitably change somewhat. Anyhow, I am having deja vu, what with the Kurds and then the Catalans making news.
I have not studied the Catalans, and I have not been able to pay much attention because I have lots of other stuff getting my attention (yeah, full profs need to remember how to say no, pro-tip deux). But I did write a bunch of stuff back when I was a junior prof that applies now. While much of it was on the International Relations of Secession (see ye olde ties that divide or "Discrimination in IR"), I did do some data stuff on separatism. One of the clearest findings then and now is this: groups that lose autonomy tend to be separatist. Oh, and groups that lose their institutional means of expressing dissent may resort to violence.
So, while the Catalans may not have played this brilliantly, the government of Spain has been dumber. There really was no reason for Spain to jump so hard and so fast on the Catalans. Before the past several months, Catalans were ambivalent about secession. How to reduce that ambivalence? Revoke their autonomy and do other things to make the Catalans feel as if they cannot exert their voice in a democratic Spain. What should Spain should have done? Arrogant for me to say from my position of ignorance, but here I go: not much. Spanish leaders should just not have recognized the referendum as happening. "Oh, you guys are lining up to vote on something purely symbolic? How cute."
What has worked in Canada could have worked in Spain: give the separatists enough of what they want that it becomes hard for them to win a referendum. Sure, sometimes you get a nail-biter, but it is easy to imagine what would have happened in 1995 if Canada had been heavy-handed. Yes, more decentralization can lead to more demands and perhaps more separatism, but doing the opposite does so more quickly and, more importantly, can lead to violence. As Spain shuts off the ability of the Catalans to win democratically, it would not be surprising if some Catalans became radicalized and started using violence.
Then again, unforced errors are all the rage these days: Brexit and Trump and now Spain v Catalonia. So, we can pile on the Spaniards for messing this up, but damn our houses of glass are broken.