This legit combo is nothing new. Of course, you have to actually read what your opponent's cards do. Then it becomes obvious what is happening. But here's a short explanation:

Laelia gets a +1/+1 counter whenever a card is exiled. Etali's Favor via discover 3 exiles cards ONE AT A TIME until a card with mana value 3 or less is exiled. The one copy of Etali's Favor is the only nonland card in the deck with that low a mana value. Therefore, all cards in the library get exiled. Nothing can be played from exile, and the cards go back into the library. Then, Laelia's many triggers (remember, the cards were exiled one at a time, so each exile creates a new trigger) go on the stack, each one puts a counter on Laelia. The card Throes of Chaos can cascade into Etali's Favor, and can be cast from the graveyard via retrace by ditching a land as additional cost, of which the player has plenty since the deck only needs those two nonland cards anyway. And cascade also exiles cards one at a time until one with a low enough mana value is exiled. So even more Laelia triggers

2024.38.40.1753.1078427 was the version

It's the log of the game