If however you are the kind of person who will emulate anything a celebrity does and one of your favorites has come out publicly about their beliefs... well I am just going to say that that is a lousy reason to choose a life style but it's not like people haven't done that for years. Drink "pop" soda, it's bubbly and fizzy just like them. 'It tastes heavenly'.
Christian influence reached it's peak around 600AD (MAP) Pretty much everything in color on the map was considered Christian; Byzantium, Roman, etc, there were 5 distinct "Bishops" at the time.
Within 150 years the landscape changed to this however (MAP). Islam had started, like Christianity, as something spread by word of mouth and a matter of personal faith but it did not take long before it was being spread by political entities conquering wherever they went. The current batch of terrorists want to bring back this particular type of rule and talk about a new Caliphate rule.
The Ottoman Empire was the last Muslim Empire and it's growth looked like this (MAP). They conquered the once great Byzantium Empire and much much more. At the same time the previous invaders were successfully pushed out of Spain. By the time they were finished however there was only one "Bishop" left (though there is again the Eastern Orthodox and that is another long story...) hence the pope in Rome. The Ottoman Empire lasted in some form or another until the mid 1900's. That is awfully recent.
If you look through the history of the entire world and not just a thousand or so in Europe (a few hundred if you are speaking of the crusades) you will find the same thing everywhere you go. Most religions begin as personal beliefs practiced at home and then become a matter of contention in larger conflicts between opposing nations. Religion is not the cause merely a piece in the larger picture of what makes us human.