My understanding is that Pascal was a much better producer than he was a director. I'm pretty sure I read that it was Shaw who urged him to direct also after Pygmalion, feeling Pascal ought to have total control. But Pascal's style of directing appears to be to work with actors and editors in making directing decisions  for instance getting director Anthony Asquith
and actor Leslie Howard to direct Pygmalion, and working with editor David Lean and actor/director Harold French to assist on Major Barbara. I don't think this style was a secret. The directing talent behind Pygmalion was decidedly Anthony Asquith, who went on to direct another Shaw play "The Doctor's Dilemma" in 1958, another success, showing it was his magic that turned Shaw's plays into cinema more than Pascal. Pascal's success was to gain the trust of Shaw and get him to grant concetions on the script. It was probably a mistake for him to direct "Caesar and Cleopatra" alone, most likely at Shaw's urging, as he didn't really have the director's skill so much as the art of the deal. But he was so afraid of losing Shaw that he most likely agreed to take total control to please Shaw. Sadly, had he kept Asquith, all his later attempts might have succeeded. Far from the megalomania that he is sometimes portrayed as, Pascal appears to have enjoyed deep collaboration, both with the playright, the directors, and the actors. Shaw came to think of Pascal as such a genius that he probably pushed him too far.