The tire died of old age. He gave his life for the safety of the vehicles driver.
Judging from the cracks that tire must be long overdue. Your friend can consider himself lucky. Should the blowout happened during a fast drive the consequences would have been serious.
But please, tell you friend to inspect the remaining tires and replace them if ...
As long as all 4 tires are the same size it won't hurt the vehicle.
The winter tires are the same width but about 43mm or 1.7in taller. This will slightly throw off your speedometer making it read a little slower than you are actually traveling.
Normally the thought is to have thinner winter tires, not taller. Being thinner helps slightly increase traction ...