Isn't there a EU regulation saying a day off is at least 24 hours +11 hours? Which can be reduced to 8 hours, so to get two consecutive days off it has to be at least 48 + 8 hours (or 11 depending on circumstances)?
What's the weekly workingtime for an ATCO in Spain? And how much overtime do they put in versus how are they paid (extra) for having to work in their time off?
There are a lot of factors that can be at play in a strike condition, and when people strike, it's usually from fatigue, stress, overload and a situation where they feel noone listens to their concerns (not complaints, but concerns, if concerns doesn't gets taken care off, they evolve to complaints, and letting them evolve is poor management, and even worse management is crying about your workforce when it has been allowed to evolve).
But noone want to hurt innocent bystanders, passengers, by striking, but what the heck do they do when noone listens? Controllers take their work serious, and usually don't stay at home to rest when they are assigned a shift.