Business class for Lau? The mileage cheat - nonsense or real?

Hello everyone, of course here in the sub, in the best case scenario, expensive vacations are avoided in order to increase the deposits into the Grail. But there are certainly some people here who allow themselves one or two vacations. Lately I've been getting more and more people in my feed who are preaching that by routing all of your spending through your credit card, you can secure miles worth several business class flights per year. Now to my question? How much is there? Do