That article claims that the "Big Whack" that formed the Moon also stripped the Earth of much of its original crust, making the surviving crust relatively thin, which then allows plate tectonics to take place.

Venus, however, had kept most of its original crust, which is too thick to indulge in plate tectonics. Thus, it has some big shield volcanoes instead, as Mars also does. Imagine what would happen if the Earth's Pacific plate was not drifting over the mantle; the mantle plume that has been making Hawaiian and Emperor volcanoes would instead make one very big volcano.