I had thought that dark matter should be responsible for only a very small portion of the mass of supermassive black holes in the centers of galaxies, for the same reason that dark matter is distributed much more evenly than ordinary matter. But it turns out I could be very wrong about this.
Researchers from the University College London modeled the gravitational interactions between dark matter halos and gas embedded in the dark matter. They found out that depending on the thermal properties of dark matter, a small disturbance could cause a rapid gravitational collapse of dark matter into a black hole. Appropriately enough, this rapid collapse of dark matter is called "dark gulping".
Dark matter being what it is, there would hardly be any electromagnetic radiation from the collapse. This would avoid the blasting away of matter by a normal accretion disk which slows down the growth of a black hole, not that dark matter would be affected by radiation in the first place. It would also explain how supermassive black holes could have existed when the universe was less than a billion years old.
If it turns out that dark gulping is indeed responsible for the formation of supermassive black holes, it could provide an interesting look into the properties of dark matter. Because dark gulping is determined by the thermal properties of dark matter, which depends on the degrees of freedom of each dark matter particle, i.e. the number of ways that a dark matter particle could move, rotate, etc., this could give hints to the microscopic interactions of dark matter or even the number of extra dimensions our universe could have.