i would say that it became political, given the fact that the rulers of the punjab were not a religious bunch and saw the gurus and their followers as trouble. actually, it's extremely similar to the situation in stuart england between the monarchs and the puritans - essentially the puritans didn't approve of the monarchs and had a large number of followers and eventually a military power base under cromwell. the sikhs, feeling oppressed and victimised, started to self-organise and turned more militant - it was out of oppression this that a militia called the khalsa (or "pure") grew, which eventually had turned into an army by the time the british had started to take over. the khalsa had turned into such an impressive martial force, trained by foreign mercenaries and equipped with the latest artillery, that it was referred to as "aldershot in turbans". they were keen to march on the raj, but were betrayed to the british by their own generals and the maharani-regent after they murdered the uncle of the boy maharaja, who was her brother. it was as part of this skulduggery that the british got their hands on the famous "koh-i-noor" diamond which is now in the crown jewels and eventually the whole punjab. i recommend george mcdonald fraser's "flashman and the mountain of light" if you want to learn the history, plus if you've never read any flashman books you're in for a huge treat.
after the khalsa was defeated at the battle of the sutlej, the sikh regiments became part of the british army - and a fearsomely effective force they were, serving all the way across the empire and during WWII. they are still a powerful group within the indian army and remain powerbrokers to this day. obviously there are a lot of people who still think that they were screwed over and want the punjab to be independent again, but they're in a minority.
so, i suppose i would say that the political impact of sikhism was almost accidental, but understandable in the circumstances and certainly had a large effect!
b'shalom
bananabrain