You can't really put this on God. In any religion there are losses of life because God cannot and will not violate peoples' free agency. Yes, he can and probably does protect some people if he has a work or some sort of plan for them; but sometimes he just lets these things happen. In other religions, people say, "Well, God needed them on the other side," but hey, how many of those 20 had spirits? Most, if not all of them, are already in Paradise from their point of view. At least that's what we're told. And if they're right, heck, I'm sure there will be a meeting nearby that they can go to.
If the leaders of the JWs say that God protects people en route to meetings, they put themselves in danger of something like this happening.