It’s a form of evolutionary cross-tolerance. The mechanisms that tardigrades evolved to handle the hydration/dehydration cycle in moss just happen to be very ef

It’s a form of evolutionary cross-tolerance. The mechanisms that tardigrades evolved to handle the hydration/dehydration cycle in moss just happen to be very effective at protecting them from radiation and a bunch of other environments. That’s not a very satisfying answer until you dig into the biology that makes it happen. The mechanisms that protect cells from environmental stress are useful for many different kinds of stressors.