I answered the "fucking question" just fine, what's your point?
But since you don't get it, here is a long explanation for you:
You have to get as much FoF procs as possible to keep up Icy Veins.
Frozen Orb gives you a lot of FoF proccs.
Blizzard ticks reduce your Frozen Orb cooldown.
So what are they doing in this log?
The Boss spawns on pull with 2 adds some seconds later. They cast Icy Veins and Frozen Orb, get a lot of FoF procs and cast Blizzard on 3 targets to reduce the cooldown of Frozen Orb.
With that they basicly have Frozen Orb available after ~30 seconds again. More Frozen Orbs > more FoF procs > higher Icy Veins uptime ... yes it's that simple.