"They just happened to know where the money was and they knew it was in monasteries and they weren't Catholic, so they didn't care."
And they happened to have the technology, open water seaworthy vessels which were still shallow draft enough to navigate the rivers to facilitate raiding inland monasteries which were the treasuries of the time. Much like the British gunboats of the 19th century, this technology permitted them to extend their raids and ultimately their settlements as far as the Black Sea, Sicily, and, of course, Great Britain and Ireland. Great Britain controlled much of Africa with those gunboats and the Vikings ultimately large portions of Europe. For example, William the Conqueror who invaded England in 1066 was actually a Viking descendent whose great-grandfathers had conquered Normandy.
A look at those ships brings back to proper usage the word "awesome" when one considers the beauty and functionality of their form. One wonders how men could stand long voyages in the open Atlantic exposed as they were to the elements and spray. These ships were truly technological breakthroughs of the age.
Few realize the there were many varieties of the vesels, each having its own purpose.
http://en.wikipedia.org/wiki/Longship
Good history here. Yep the Norman French originated with the invasion of the North Men. A truly ambitious and enterprizing gene pool that spread through Europe, likely the engine that fired the Renaissance and brought on the Industrial Revolution.
Had the rest of the world been gifted by Viking invasions, there would be less sloth and poverty. Hmmmm! Did the Vikings ever invade Japan?
In short, they were smart. And accomplished. And ambitious.
A good combination to build a civilization where a civilization needs to be built.
Norman-dy.......or North-Man-dy. And in true Viking style, William ravaged the English countryside in 1066. So even though King Alfred's Saxons kept out the Viking raiders, the Vikings thru their descendant William of Normandy eventually ascended to the English throne. William the Conqueror, believe it or not, is an ancestor of Prince Charles :-)
Even more amazing is that the Norse lacked saws, compasses, rulers, nails, screws, etc.
Every ship was built using only eyesight and experience to measure and cut the pieces that would fit together to make a watertight, seaworthy vessel. The knowledge was passed from generation to generation through long apprenticeship. They had no manuals on "How to build a Viking long boat".
The very shallow draft of the Viking ships was useful also in France, where the Norsemen navigated far up the Rhone river into the heart of the country; whereas most ships would have been stopped by the many bridges they encountered, the Viking ships just sailed beneath them.
When necessary, the ships could be partially dismantled and carried from one shallow body of water to the next navigable river, as they did in Russia in order to reach the Volga and the Black Sea.