- here we go again - that makes NO sense!
It reminds me the first time I wrote about "101" using RA. Your reaction was quite similar.
Even if it doesn't make sense, it's close to what was done by "044". As we can exclude technical problems, UFO, and many other media theories, I would say the root cause of the crash was ingnoring the rules and some unorthodox airmanship.
Now going back to RA. First I was thinking it was a crew error but after checking the Tu-154M FM I'm not sure anymore. The landing procedure requires to switch from barometric to RA starting at 60 m altitude and read height every 10 m down to 20 m, and every 5 m starting from 20 m.
Now, we have 2 options.
A. They switched to RA because they were lost, went insane, etc...
or
B. They switched to RA because they were following the landing procedure (or a part of it).
Anyones choice.
If "B", knowing how inaccurate could be an NDB approach and the weather conditions, they had to rely on GPS/FMS to attempt a landing. I see no alternative. We also know from the interview that Yak's crew probably did something similar, by the way ignoring a Go Around (twice?) from Smolensk ATC.
Just my theory.
Arrakis