I think the main purpose of the eu is to prevent the triggering of a III WW in Europe. To ensure peace, the EU has worked in these years by linking all of the economies and political systems of member states. So making the economy thrive is a way to achieve this goal, it is not, as others have written, the main purpose of the european union. At all. The eu has much much different ambitions. If in its work, it makes people richer, the better, but in order to get into the EU a country doesn’t have to be rich, or big or christian, or strictly with a european territory or anything of the sort.