It is very hard to track animals in the middle of a snow storm, especially if they got a head start. Here is a scenario. Otzi is packed and ready to travel. Has his gear, spare food, weapons, etc. Someone wants to get his stuff, for any one of several reasons. They shoot him with an arrow, but he runs off into the woods. The shooter is not dressed or equipped for a hunt. He runs for his buddies, they have to get on their cold weather gear and pick up food and weapons. It takes a while to get organized so even if they track him for a while, it gets dark and they can no longer follow. It is still snowing, so even if they camped overnight it was almost impossible to find and follow a trail especially when he was up in the rocks and craigs. So he traveled as far as he could, then collapsed and was covered by snow, and thus never found. Wasn’t he in a depression where he ended up frozen for 5,000 years.
I don’t buy it.
I think what really happened is Otzi stumbled into some information damaging to stone age Hillary and ended up suicide-ing himself with an arrow to the back.