How did Hubble observations change the scientific consensus regarding supermassive black holes?

They provided evidence that supermassive black holes are a standard feature found in the hearts of most galaxies.

Before high-resolution optics allowed for detailed study of galactic cores, the presence of supermassive black holes was largely a theoretical hypothesis. Observations enabled astronomers to see into the glowing centers of galaxies, which previously appeared as a blur. By measuring the velocity of gas disks swirling near these centers, scientists calculated the immense mass of the central objects, often millions or billions of times that of the Sun. This confirmed that these black holes are not rare, but instead grow alongside their host galaxies, influencing the shape of the galaxy and the rate of star formation.