The phrase
"unexplainable reason" means that there is no logical or clear explanation for something that happened or is true.
Full definition
And there's somebody — or something — out there who for some irrational,
unexplainable reason is killing us.
Also, for
some unexplainable reason, attacks are sometimes split up between different monsters instead of concentrating on one foe at a time.
A book that simply explains
the unexplainable reasons of Vietnam through the telling of the life of John Paul Vann.
For
some unexplainable reason, my eyes find that book wherever I am, whether it's in a crowded Tesco or on the shelves at Waterstones.
Worse, for
some unexplainable reason, the hosting of my blog fell apart two days ago, and not for any change that I made.
Also, for
some unexplainable reason, attacks are sometimes split up between different monsters instead of concentrating on one foe at a time.