potatoes could be grown in Europe, and therefore caused something a food revolution.

Up until this point the staple food of Europeans was grain (and products such as bread), this was only harvested in late summer/Autumn

Potatoes could be harvested much earlier meaning there would be less of a gap in food production.

they also did not require as much preparation, like when we compare making bread, to cooking a potato.

if you want to learn more there is a book called the history and social influence of the potato

Potatoes are exceptional as a source of vitamin C.
They don't contain cyanogenes as a antinutrient like yams (their strong lectins are degraded by heating and solanin is little enough to allow a potatoe staple).
They grow in middle Europe (als /u/thepioneerlemming said) and they grow on poor soils not suitable for grains wheat.