A car may be safer than a mobile home during a hurricane because they are usually lightweight structures that can withstand high-velocity winds that accompany hurricanes and tropical storms without being pushed off blocks or collapsing.
As opposed to houses built on concrete slabs which are usually built with utility systems that are nailed to the foundation, mobile homes have no load-bearing walls or systems attached to their slabs which makes them more susceptible to being lifted and blown away by hurricane-force winds.
However, that does not mean that they can simply withstand any amount of force. If a car is hit by a tornado and gets pushed into another object (like a house), it will most likely be destroyed as well, but studies show that cars generally fare better than houses during the hurricane.