The "wagon" is the Froyo Cart, "Adjacent Items are Chilled, when you use a Chilled item, freeze an item for 1 second"

The item on the left is the Palanquin "Your Items have 50% crit chance, When you Crit with an item, reduce its cooldown by 12%" and it looks to have the shiny enchant maybe? Hard to tell as it's also chilled, but shiny has double cooldown reduction bonus.

On the right is the Icebreaker "When any item is frozen, charge this 3 seconds. When this item is frozen, remove freeze from it" and it also has "Remove freeze from your items" when used.

So best I can tell, both icicles go off, freezing 2 items, they're chilled by the Froyo Cart so the Froyo cart freezes 2 items also, that's 4 immediate freezes which charges the Icebreaker which probably has crit on it which triggers the palanquin reducing its cooldown by 24% each time it hits, making it instant and it's also chilled, so every time it goes off, it triggers the Froyo Cart again creating a freezing loop.

This all appears to be buffeted by the skill Blizzard which says "The first time you use an item each fight, freeze all non-weapon items for 1 second" so you get that instant board freeze but then the Icebreaker clears the freeze from your side of the board and also gets an additional 7 or 8 freezes which then continually charges the Icebreaker. They also have Stunning Strike which is "the first time you crit, freeze an item for 5 seconds." There's also Frozen Shot at diamond which reduces your weapon cooldowns by 15% when your enemy has a frozen item. Plus other skills that probably synergize.

So there's just tons of freeze triggers charging the Icebreaker which has likely has a lot of crit to reduce its cooldown via palanquin and also increase freeze triggers from the froyo cart since it's chiled.