On why buddhist monks might of felt the need to develop a martial art. What better way would there to influence and get the respect of the warlords and generals of the country?
You develop a martial art that serves the greater good not only on a personal, self defense level, but through it you can attract and influence those who are interested in war and destruction. Teaching them your masterful forms of combat might influence them. The very temple surroundings with its calm atmosphere and peaceful monks would also temporarily calm them and help them see an alternative life to seeking war and conquest. Unbeknown to the generals that the same qi gong and forms used for combat are also burning up bad karma by flushing their energy systems with positive energy and flushing out the negatve.
Not only that. As Doshin of shorinji kempo found. The martial arts attract you young who do not want to sit and listen to boring religious doctrine. However, shorinji kempo is well entwined with Doshans own take on Zen.
I wonder how many folks have taken up martial arts and then looked into the more spiritual aspects as time progressed. I’d say a hell of a lot more than in any of other physical activity or sport.
I don’t like to admit this but also. It is possible that the shaolin temple was merely corrupted and that chan was used much as it was in Japan by the samurai. Is there any evidence of this?