User blog comment:Le Rottweiler/Can Shubby use mind control?/@comment-26005008-20150414125515/@comment-3547390-20150414132614

Probes are traditionally mechanical, but you are still thinking in human terms. Realistic... human-like... you have to learn to get past these words to start understanding the unnamable!

Well, according to the story, Ranger just happened to be at the right place at the right time (away from the base). As for the logic why they didn't hit Ranger when he came back, I do not know. Perhaps Shub-Niggurath wished for a challenger.

I have a belief that goes a bit further, but it is almost entirely unsupported by any sort of logic. I think the infection was man-made, but that the thought of it came from Shub-Niggurath. The missing piece of the puzzle is why Ranger was not attacked.