The in-built ramp and card selection of Thrasios allows you to always find the right card, and Vial Smasher is a win condition in and of themselves
Later in the game, you can even switch over to getting colorless mana and stop losing life
That means nobody can counter it, and you can very easily put in a Creature you cant afford otherwise
On the one hand, they die to board wipes, and on the other hand, they also synergize with creature-based strategies
On the front side, he's already doing quite a lot for just : he has Lifelink, comes with a relevant graveyard-hate clause, and generally does a good job of being annoying in all the right ways
Dragons Rage Channeler can often single-handedly enable Delirium and an early Murktide Regent while also getting in for three damage consistently