Pure speculation regarding this tragic case, but I was reliably informed a few years ago that to fly in certain parts of European airspace, A/C above a certain weight/seat allocation had to have TCAS fitted.
It was believed that some airlines fitted the kit to permit them to fly in said airspace, but did not train the crew in the correct use as that would have added more expense.
I am not in any way saying that this is what happened here - but in a regime whereby authority is everything and a way of life, it must be difficult, especially with regards to newish technology, to ignore commands/instructions given (in good faith) by an ATCO etc.
Fortunately, as Lon alludes to, Crews and ATCOs are now more aware of what should happen during a TCAS event.
Although a horrific incident, is a court case and possible prison sentence the best way to end this? Open reporting of incidents is what is needed - the threat of disciplinary action, either by company or courts, is not conducive to this.
Also, so many years have passed, and the ATCO involved is no longer with us - this leaves an instant and convenient scapegoat, which may mean that the truth, and indeed lessons to be learned, may never surface.