Electricity can leap through empty air, switch is off position does not guarantee electricity is not strong enough to leap through and pass to other sensitive electronic equipment. Empty air just have very high resistance value only. The more resistance you create between the electricity source and the equipment, the harder it is to reach the equipment, such as pull the plug. But a direct strike onto your house and through the window still probably can fry equipment even if unplugged.

Nothing is guaranteed in the natural world. The only ultimate mitigation method is to save spare money to buy a new one in case of kena murphy's laws.