I think the causes of this accident are actually pretty straightforward, and you can find them out reading some statements from the Yak's crew that landed shortly before the crash. For example "facilities at the airport worked incorrectly which can be established from the fact our GPS was off the mark during the approach. Had we flown by the GPS, we would have ended some 50m off the centerline". Poor training, zilch experience, they simply shouldn't have been allowed in these cockpits.