Damage analysis: spark plugs finished after one year

Moin people and a happy new year, I made my `96er 855 10V fit over the winter and rolled a few days ago fault-free through the TÜV. However, I didn’t even have the 2km home with it anymore. First there was a slight jerk, followed by the polter bumping detonator and shortly afterwards he went out and was not able to get any more. I quickly got back to the workshop and left the car there over the weekend. According to the workshop were the candles and a torn cap of the culprits. Strange is, however, that I changed them exactly a year ago (original Volvo ZK and a Bosch distributor) and the car before the visit in the workshop was super started and very cleanly purred. The car was to the TÜV in the workshop and got there also a new VDD. How can the candles after >10tkm and 80% long distance be so ready that the car is not even to move? I would be very interested in your opinion on the topic.