Europe is a continent consisting of developing nations and bitcoins was developed in this continent too. It's the home of bitcoins.
Reasons behind its development is because it's completely being legalised in most of the countries there. Countries there are now trusting on bitcoins thoroughly.
Most of the oil and reserves in Europe are now using bitcoins in their business. Government of many countries in Europe are also planning to legalise bitcoins for use in parliamentary affairs ( just planning, not sure whether they will allow or not). People also priviledge bitcoins more there..
And these are the primitive reasons.