If, and that's a really big IF, those two clubs are not fighting off relegation within the next 3-5 years, we will know if it's truly luck or not.
I do find it a little amusing that people believe with clubs like Madrid, Bayern, City, etc that effectively have limitless resources, there is any merit to Brighton/Brentford/whoever has outsmarted them, found some secret sauce they haven't. It's just a good set of things put in place, with right people and a little luck in timing, over time the ratio of hit/miss will return to mean and the only way to compensate for that is having more budget so the misses don't matter.