Pointless speculation about why this plane crashed serves no good purpose
The plane crash in the Alps brings to mind a (possibly apocryphal) story about a newspaper editor 100 years ago asking an astronomer to write a piece on whether or not there was life on Mars.
The astronomer said nobody knew. The editor asked him to provide 1000 words on the subject. Several hours later he received the astronomer's work: the words 'nobody knows' written 500 times.
So it is with the plane crash. Acres of words have been written, all saying 'nobody knows'.
It could have been explosive decompression. It could have been oxygen hypoxia.
It could have been a stall. It could have been catastrophic mechanical failure. It could have been controlled flight into terrain.
It could have been pretty much anything that has ever caused a crash. But at this point we don't have the slightest clue.
And the speculation is not healthy. It makes it seem like aviation disasters are common. Thankfully they are not.
In fact, one commentator put it in perspective beautifully.
If we had the same accident rates as 1973 with today's number of planes, one commercial jet-liner would crash every 41 hours. Accidents now are extraordinarily rare, multi-causal usually complicated.
So let's cool the speculation and accept that at this point, no matter how many times you guess at the cause, nobody knows.