Without looking at the video it looks like a Hammer Throw proccing Smite. Look at the two middle idols and what they do.
This build is reliant on having at least one Adorned Rahyeh Idol, to procc Smite on hit with throwing attacks.
If you’re in the Merchants Guild, you can easily buy one.
If you’re in the Circle of Fortune, stack Adorned Idol Prophecies.
This is no dedicated leveling build. You can level with the same skills but it’s a lot slower and deals less dmg untill you get the needed idols. With the rarity of said idols you have a lot to do untill you make it work properly.
Though levelling with casting Hammer Throw/Smite manually isn’t particularly slow IMO. Hammers are good for trash/clear & large bosses.