Am I right when I say that this is a pretty huge coincidence? As far as I can see Soyuz rockets almost never fail and Proton rockets only fail from time to time.

Excluding this incident, Soyuz rockets had one partial and one complete failure during the last decade (and more than 115 flights during that time). The variant that is now used exclusively for manned flights had 33 flights and no failures. Soyuz-U – the variant used for this flight – seems to be the real troublemaker. It’s responsible for the only other complete failure during this decade.

Proton had more than ninety launches in that decade and five failures.

Those Russian rockets are very mature and usually don’t fail.