It'a because it developed completely separately. Philosophy started with the Greeks and has been continously developing from there ever since. The Chinese had their own cultural sphere which developed on its own, with no influence from the West until very recently.
Just to clarify, I'm not try to be an edgy racist memster. Arab and Persian Muslim thinkers, for example, are also philosophers.
Buddhists worship Herakles and the Buddha is a Christian saint.
More generally, Christianity reached China, and Buddhism reached Greece.
Sure there were some contacts and influences, and you even had some very influential philosophers like Leibniz who were hardcore sinaboos, but the two more or less developed separately.
As for Buddha being saint, so is like almost every other pagan deity out there. And those who aren't are demons. That's just a Christian thing.
Army officer here, the books is good. It's pretty obvious stuff for nowdays, but back then it was probably revolutionary