Can someone help me figure out what's going on in this build?

Looking at this guide on maxroll : Tempest Earthquake Beastmaster Guide - Last Epoch
I was trying to figure out what is casting the storm bolts, I know maelstrom is being used as part of Warcry and that’s not included in the guide, but I can’t figure out how the bolts are being cast.

The procs from tempest strike give you the storm bolts (pretty sure).

I’m using tempest strike but no procs for me, it’s possible that it happens with 8 stacks of maelstrom but I’m not sure.

just look at all the little tree nodes. you might not have it yet or picked the wrong one.

I want to say the game play video is outdated and Tempest Strike was reworked or the build was updated due to nerfs/buffs. As soon as you take Grounded Refuge, it removes the lightning strike.

Maelstrom won’t have lightning hits. Could also be an idol.

So, it looks like once you have 8 stacks of it you get storm bolts, I could be wrong, havent had a chance to test it yet.