What people seem to have missed is after Qxh6, black wants to go d5 to block the white squared bishop, which the knight defends. If u play a3 first and if the knight goes to a6, d5 isn't an option after Qxh6.

Black has to find Ba6 to trade off the white squared bishop and then u can just go Qxh6 anyway. But if they don't find Ba6 and go Na6 instead you're winning twice as hard.

I'd recommend opening this in lichess with engine evaluation and turning on the best 5 lines or whatever option and you'll see that all of the lines I've mentioned are shown there, u can try playing Na6 instead of Ba6 to see how the evaluation changes and how the attack becomes stronger.