Wouldn't all forming black holes become huge ring of matter orbiting its common center gravity instead ?

Your doughnut would only form if the centripetal force was greater than the self gravitational force that is causing the collapse. Since the gravitational force supplies the centripetal force , it is not possible for there to be sufficient force ( at least from gravity ) to form a torus. A ring is possible, as tidal disruption ( caused by differential gravitational attraction ) can catapult small mes into stable orbits, at the expense of similar mes being "absorbed" by major body.