Im betting the engine had a ton of idle hours along with no oil changes. Ive seen worse engines that were still running. Likely it was getting hot rodded and the pickup tube clogged up causing the engine to loose all oil pressure or goop pressure in this case.
Engines can run a surprisingly long time on no oil changes. Some believe it is a waste of money and just top engines off.
About 5 years ago i bought a 2004 F150 with the 5.4l in it. The truck had a mis in it and 118k miles. I got it super cheap. I figured they broke the plugs off and didn't know how to repair it. I got it home, extracted all the plugs with the mac tool plug extractor, installed new plugs changed the oil to motorcraft and it ran beautiful.
I noticed it had a little chain noise when cold so i figured the guides were getting weak. a few days later i was pulling into traffic and had to stand on it. It ran great until about 5k rpm and the engine just cut out, the ecu cut it to and idle and it was rattling and shaking and lost oil pressure. truck was still running so i put it in nuetral and shut it down coasting on the shoulder. I let it sit for 10 mins as i thought it may had been sludged a little as i only found receipts for 3 oil changes in 118k miles from walmart. it was serviced when the brakes were replaced at 35k miles, when the tires were replaced at 68k miles, and when it was taken in to have a tire patched at 115k miles. I started the truck up, it got oil pressure and i drove it home.
I took the front diff out, dropped the pan and found 2 inches of sludge. pulled the valve covers and all you could see was a path where the cam lobes had kept the sludge back from rotation, front cover was the same. only had a path for the chains through the sludge. I cleaned out the pan, replaced the pickup tube, oil pump, chains, guides, guide tensioners, cam phasers, and lifters. the cams and rockers i soaked in chem-tool. I sprayed 3 cans of oven cleaner in the heads on top of the sludge and let it sit over night. came back the next day and pressure washed the heads clean.
I checked the bearings and they were surprisingly still in good shape. i reassembled everything, put fresh oil in it and drove the truck until it had 168k miles on it doing 3-5k mile oil changes. I have a UOA i posted here of that engine when it had a 144k miles on it and it was beating average wear. I sold the truck to someone local who still drives it daily. The last time i spoke with him it had 208k miles on it.
The point in all this is to say that many engines can last a very very long time on and oil change if they are topped off and not hot rodded while sludgy. Im betting you could take a new car with and engine that is easy on oil, change the factory fill in it at 10k miles and put in any good modern synthetic in it, top it off when it needs it and the engine would still run perfectly fine at 75-100k miles. you could change that oil and sell it and no one would ever know. That would be pure evil by BITOG standards, but it would likely be feasible.