The RPG fuse works on an electrical current that passes through the sheetmetal nosecone. If the sheetmetal nosecone gets dented, it can ground out on the inner metal liner, causing a short, which renders the fuse dead.
This is why we used chain link fencing in Vietnam against RPGs, and why the fence on the Stryker works. The Brits also used steel mesh around their lookout towers in North Ireland, and I remember civillian cargo boats on rivers in SE Asia (in areas of pirate activity) equipped with mesh for the same reason.
It's a well known, cheap and effective counter to the RPG, that simply has been resurrected due to circumstances.
The nosecone fuse problem is also why there is such a high dud rate with the RPG. Because the nosecone is always exposed, both in the launcher and in the carry bag (three rockets in a bag on a guy's back), they easily get dented and rendered duds.
Ross