I am not saying it is true in this case, but when the tape snaps the tension from the supply reel slaps the end pretty quickly on the the take-up reel, or vice versa.

I did recording for my stuff on a reel to reel, and scrambling to get to the stop button before the tape slapped itself apart was just a thing you had to do, with old tape.

It is not that the plastic backing fails repeatedly, but that oxide gets slapped off the backing as the reel slaps the broken end on the other reel.

30-40 bits of oxide falling off is entirely reasonable.

I cannot imaging you could actually get it back into playable shape though.

It could have wrapped up a segment of tape and broken several layers once siezed.

We have to remember that the media used at the time was not the same mass produced cassettes we were exposed to in the 80s and 90s. It's very likely that the material was far more brittle back then.