How come you have to train under a Gracie?

To be considered legit you don't have to train under a Gracie, all you have to do is perform well at competitions.

1) You don't have to train under a Gracie. But if your lineage doesn't somehow end up with someone named "Gracie" you're not doing legit BJJ.

2) By your own admission, your knowledge is limited. Perhaps some of the techniques ARE easy to do; certainly some of them are common in most grappling systems. However, the flow of BJJ, the actual ground grappling ability, is not something that comes easily.

3) On a conceptual level, anyone with a Judo/Jujitsu background COULD replicate BJJ. However, due to its competitive format, BJJ is constantly evolving. While most people with a grappling background could, for example, understand how the X-guard works, it's hardly the same thing as knowing when to use it. I mean, conceptually, Judo SEEMS easy, but you have to practice for years to get the feel for the movement, to feel your opponent's balance, to anticipate where their weight is going, to develop the timing you need to enter in, etc. Until you put in your time on the mats, doing Randori, you're just not going to "get" a lot of what's going on. Easy to understand, yes. Easy to put into practice, no. Same thing with BJJ.

No one said you have to train under a Gracie. I mean I love them, but that doesn't mean you absolutely HAVE to train under them. There are many other professional bjj artist that can train you.

Because the Gracie family pioneered BJJ and it is an art where instructor history (X got his black belt from Y who got his black belt from Bubba Gracie) is very important.

-- MrJM

The Gracies have excellent teaching methods, but so do alot of other people.

There is nothing magical about the Gracies, but they devote themselves fully to developing the art.