andrasz, only reliable part about explosion version I can guess is that there is no traces of missile damaging elements found on debris. So it's why Rosaviation denies Kolavia statement that "plane was damaged from outside".
A Russian government that was not entirely committed to truth-telling
might want to depress speculation by its citizens that Russia's recent moves against ISIS had invited this result, though.
Probably, at this point,
everybody is saying what serves them best.