Thats already card advantage, and your commander just stays on the table if your opponents dont have artifact removal, threatening all manor of infinite combos, and sometimes even attacked as a large threat
The rest of the cards will be put on the bottom of your library in a random order
You can also include Rhystic Study in that list too
But, I try not to assume too much nor presume to have a firm grip on the cosmos, the world, the current American political regime, or opening seven draw probabilities
Then, in addition to the free spells, you wipe the board, too - Because whatever you cascaded into (or anything else you've happened to cast that turn) will damage all opposing creatures equal to their CMC
For Hearthhull, I think it comes down to the fact that this deck is dumping tons of lands into the graveyard and it most likely wins the game by bringing them all back in one go - using a card like Splendid Reclamation - for a mass of triggers