It is certainly not a recent trend that great actors devote themselves to a directing career. This trend has existed since the dawn of cinema, with silent films, and moreover, it is something that happens everywhere in the world, not just in the huge Hollywood show business.
Having been great actors, however, is no guarantee of becoming great directors. There are some exceptional cases, with actors who have become perhaps even greater behind the camera (Clint Eastwood, John Cassavetes, Charles Laughton, Charlie Chaplin), but not all of them make it to the Olympus in both roles.
Perhaps, however, the role of director is not immediately apparent to the general public, so it may have escaped the notice that these 10 great actors are also great directors.