Black holes at the centers of galaxies, known as supermassive black holes, do have a strong gravitational pull. However, there are several factors that prevent them from simply "swallowing up everything" in the galaxy:
Stable Orbits: In a galaxy, stars and other celestial objects generally have stable orbits around the central black hole. These orbits are determined by the balance between the gravitational pull of the black hole and the objects' own momentum. As long as these objects are in stable orbits, they can continue to revolve around the black hole without falling into it.
Size and Distance: Supermassive black holes have immense gravitational pull, but they are also relatively small compared to the overall size of a galaxy. The central region of a galaxy where the black hole resides is typically a small fraction of the galaxy's total volume. Therefore, most objects in the galaxy are far enough away from the black hole that their gravitational interactions are dominated by other nearby objects, such as stars.
Accretion Disk: Supermassive black holes are often surrounded by an accretion disk—a rotating disk of gas and dust. As matter falls into the black hole, it forms this disk. The accretion disk releases energy in the form of radiation and powerful jets of particles, which can create outward pressure and counteract the inward pull of the black hole's gravity. This process helps regulate the growth of the black hole and prevents it from swallowing up everything around it.
It's important to note that while black holes have a powerful gravitational pull, their influence is limited to a specific region around them. Outside this region, the gravitational effects of other objects dominate, allowing galaxies to maintain their overall structure and preventing the black hole from engulfing everything in the galaxy.