Spontaneous (Sort Of) Blowouts

Years ago when my family was in the broiler egg production business, we hired a couple to help gather eggs and sort and clean them. The man was a midget with a sour outlook on life and his wife was a very fat and jolly woman. They parked their car in front of the egg house and one day it was just sitting there and one of the tires blew out Everyone raced out to see what had exploded and the dust was just starting to settle when a second tire blew out. As you can imagine Mr. Sourpuss took a very dim view of these events, but Ms. Jolly laughed till she doubled over.
Hiram has a cheap bike he got at Walmart. He is a large man and maybe should have had a better bike or at least wider tires. One day after he had come back from a ride and parked the bike a tire seemingly spontaneously exploded. I thought it was pretty hilarious, but he did not.
Virgil drives an 18-wheeler, and on a recent day the brakes on the trailer locked. He called in to the office and they told him to just drive on in and they would fix it. (What dummies!). He decided to stop by a farm supply after he had driven for a while. As he was climbing down from the truck, one of the tires exploded with a cannon blast. When he saw what had happened, he went in the store and while he was there, a second tire exploded.
The moral of these stories is to keep a close eye on your tires and don’t drive balloons. Oh yeah. And don’t drive with the brakes locked.
While it is lucky that none of the people in these stories was driving at the time of the blowout, it does seem odd to me that the blowouts all occurred after the vehicles were stopped. Is this serendipity or is there some law of physics at work here?