The whole Hubble mirror fiasco was fascinating. The before and after images of the galaxy M100 in the following link outlines the extent of the error:

https://www.nasa.gov/content/hubbles-mirror-flaw

One may assume that maybe the error was simply too big and that's why the aberration. Here's the root cause and the magnitude of the error would be dismissed as nothing by most people on this planet but ultimately turned out to be huge!

"Ultimately the problem was traced to miscalibrated equipment during the mirror's manufacture. The result was a mirror with an aberration one-50th the thickness of a human hair, in the grinding of the mirror."