He didn't think he could create geniuses, he thought that if you put all your focus into one thing at a very very early age, you'd be good at it. Which isn't a unique idea...
Polgár was born on 23 July 1976 in Budapest, to a Hungarian-Jewish family.[13] Polgár and her two older sisters, Grandmaster Susan and International Master Sofia, were part of an educational experiment carried out by their father, László Polgár, in an attempt to prove that children could make exceptional achievements if trained in a specialist subject from a very early age.[14] "Geniuses are made, not born," was László's thesis. He and his wife Klára educated their three daughters at home, with chess as the specialist subject
Having three daughters he trained in chess is less impressive than pretty much any other specialization.
The biggest roadblock for women in chess, was high ranking men refused to play them. And pretty much the only way to get really good at chess is to play people who are even better than you.
It's no coincidence the youngest ended up the best, her oldest sisters were there for her to practice against.