Right, counter-intuitively... As long as we'll be making up reasons based on that piece of data, how about this:
Global synchrony occurs when a brain is recovering from an unknown or detected bad state, and all major parts of the brain say "HLO" to each other to notify for their existence, proper operation and to establish connection. So it's not that it's bad to be synchronous, but the lack of information from critical parts of the brain causes it to repeatedly reboot in order to recover from a bad state forced by electric rods in the brain.
Hey, I'm a scientist!
Seriously though, why aren't we thinking about what the implications of our experimental data would be on a distributed computing system, which our brain is, instead of giving silly "it's like the key in a car" explanations, assigning causality randomly and without merit?