Diversity could have worked if only governments had the spine to tell newcomers they were welcome and would be assisted but that a few very specific and malignant ideas that helped ruin the countries they were fleeing not only were not welcome but would be grounds for a very rapid expulsion. Unfortunately the invertebrate governments of Western Europe weren't up to the task, instead producing outcomes like 'Muslims Against the Crusades', Londonistan, Molenbeek etc