I’ve flown both the receiver side and tanker side in the 135. It’s unlikely the receiver performed the wrong actions as receiver during a breakaway and flying AAR autopilot off generally resulted in a more stable platform than autopilot on. The most likely scenario is a fatigued receiver crew (when this capability is used operationally it tends to result in very long and busy duty days) tried to expedite the refuel and came in way too hot for the contact, under ran the tanker and struck the tanker with their vertical stabilizer. A B-1 did this to a tanker almost 40 years ago and the tanker crew was lucky to be able to land the jet.

All of the above is pure speculation. Could they have gone beak to beak in an EMCON environment that made things more challenging? Maybe, but somehow Kosovo happened with no midairs. My bet is the USAF decided to utilize an under resourced and under manned capability more heavily than they should have. Six Airmen are dead as a result.