One way to estimate the black hole mass in quasars is to use the Eddington Limit. Remember that this limit describes when light pressure is so great that it exceeds gravity. Clearly, our mass infall idea only works if the gravity is strong enough to overcome the light pressure. The idea is that Gaseous material is 'fed' to a central black hole through an accretion disk. The disk glows to produce the high luminosities as matter moves from large distances to small distances from the black hole through the disk thereby heating the disk up.
Magnetic fields channel some gas along the axes to make the jets.
The zoo of active galaxies arise because of differing black hole masses, feeding rates, and viewing perspectives.