after spending 30+ years of running my own shop and several years prior to that building,rebuilding and repairing gasoline engines, your photos are sights I have seen many times. The answer as to how that happens, is simple. DONT CHANGE YOUR OIL.
A man I knew bought a new mercury and never changed the oil, at 78k miles, it would not start. It was towed in and when we took the drain plug out, the oil would not drain, we put a screw driver in the drain, and pulled it out, the oil was so thick it would not even fall off the screwdriver shaft. this is a true story.
now you can tell us anything you want to, but the proof is in your photos. That engine has been severly neglected, go buy anything you want to, and neglect it, and the results will be the same.
I have stories that would blow your mind.... people are dumb, and then try to blame something or somebody for the failure.
Here is my A in front of my rinky dink repair shop, you can see all 7 stalls, singles and doubles.
sometimes I still miss it