Why does the ellipitical galaxy have a black hole in its center?

Answer 1

Scientists believe that a great may of the galaxies of all types may have black holes in their centers.

One of the reasons is that most things in space, including most galaxies, rotate. (If they were standing still, their mutual gravitational attraction would drag them into each other.) We can sometimes measure the speed of the rotation, and calculate how much mass the galaxy must have in order to hold itself together - because rotation tends to pull things apart.

For most galaxies, we can't see enough mass to hold them together. Gravity is the "glue" that keeps spinning things together, and gravity comes from mass. So the only thing that holds those spinning galaxies together would be "invisible" mass. Some scientists have theorized about "dark matter", adding mass but being invisible. Black holes also add mass, and aren't visible, and are the simpler explanation.