Why are there so many styles out there?
Because everyone is different. What works for one may not work for another.
So when someone finds something that works for him, he practises it. And passes it down. If it suits his student, that student passes it down too, forming a style. And because everyone is different, we have so many styles. Even within the same style, every practitioner is different, adapting small portions to suit him or herself.
Which brings us to the question: is there an authentic style?
People claim that what they practise is authentic. "This is how the founder practised it." "My teacher's lineage is so and so, right to the founder himself."
Yet, do authenticity and lineage mean something is practical and can actually be used?
Maybe styles that are passed down are just broad systems. Each style works for people within a certain category. But in order to be effective, the style still needs to be assimilated into oneself, and adapted to one's needs, characteristics, strengths and weaknesses.
So maybe authenticity and lineage are important, but what is even more important is to eventually bring everything within oneself to create something that works for oneself.
Because we are all different. And that's why there are so many styles. Because there are many categories of people.