A tombstone may be heavy for a human, but to a car, they’re relatively lightweight. Cars are very strong, you see, so something heavy like a tombstone is no match for them. All cars find tombstones to be lightweight and easy to transport.
What do you wish you had to transport this tombstone? Oh, that’s right – a car (かる). If you had a car, this tombstone moving business would be no problem. To cars, tombstones are naught but lightweight pebbles!