Zan and Zu Pike
I get asked this now and then -- where do new arts come from? -- and while I can't get specific about most martial arts -- speaking here of older ones, not those of recent creation -- I can get general.
Generally speaking, a martial art can arise from all kinds of reasons. Probably the most likely are 1) a perceived need for something better or 2) a philosophical shift in the mind of a player.
For example, if you live in a culture where everybody is forbidden to carry any kind of weapon and few people carry them, what is apt to develop is different than it might be in a society where everybody hauls a sword around or is packing a gat. If every man-jack and his kid sister has a knife tucked into their sashes and a razor in their shoe, it would behoove one to come up with methods to deal with short-blade attacks.
Yeah, I know, well ... duh! but some folks don't see the connection. I have heard from more than a few martial artists in the US of A who have allowed as how they don't carry any kind of weapon other than their bare hands, and they won't -- don't like 'em, don't see the need.
If they are that good, I surely don't want to mess around with them. I suspect most of them are less adept than they think they are.
So a stand-up only fighter runs into a grappler and gets his ass handed to him. Surely anybody who wants a functional art in that circumstance is going to try and come up with ways to deal with wrasslers?
A fighter from an art that favors kicking range might have trouble if he runs into somebody who prefers elbow distance and who can get there. And in order to get there, the elbow guy has to figure out how to get past kicks, too.
On the philosophical end, you might have somebody who has a workable system, but who looks up one day and realizes something about it limits its attractiveness. An art that needs speed and power probably works better when you are twenty-five than when you are seventy-five. At forty, you look up and wonder if you will still be able to do it thirty or forty years down the line and realize that if you can't, you better find something else. Or alter what you have and make it something else.
An art that offers extreme violence might run afoul of a mindset that wants to do minimal damage to an opponent. You injure somebody gravely, and it bothers you. So bash-'em-with-a-brick morphs into toss-'em-into-a-soft-lawn. You can make the change from a jutsu into a -do. Maybe you don't need some of the tools, so you stop working with them. I understand the early judo players were every bit as kick-ass as the ju jitsu players for most places they needed to be.
You either have to adjust your opponent, or adjust yourself, or some combination thereof, and if he's waving a knife and your art doesn't have a way to deal with that, something has gotta change.
See a need and deal with it. And if the current method isn't doing the trick, you try and come up with a better way.
Beat a better path and the world will build a door to your mouse trap ...