Because I ride the bike hard and don't like to die in the canyons. This is not the first issue I have had with the chain and sprockets. After the first set went at 5k we adjusted everything after every ride and repeated the results to rule out bad adjustment intervals.
Alright lets see if I can work you through all your questions here. You state the chain is of good and proven quality but it is discontinued by DID. It wasn't derailment it was a break and not at the master link. The road was clean asphalt and not all messed up. The the chain and sprockets had...
So I found out the hard way Indian didn't quite pick the right stock chain for the bike. And before we go through the normal questions: yes it is serviced and tension checked regularly. And the chain and sprockets had about 1000 miles on them.