Take length of rope, chain, cable or whatever. DOUBLE that length. If you are not actively involved in the recovery, stay THAT far away from the vehicles.
We used to teach field recovery of armored vehicles- using one or two to recover the third. Once hooked up, before you take a strain, get INSIDE and CLOSE and lock the hatches.
That gent caught a bumper, and was damned lucky. You should see what 1/2 in wire rope can do when it snaps under load. Get in the way of that and they can bury you in two coffins.
What we have here is... failure- to communicate.