IMO, the vast majority of people that found their own hybrid art do so to try and make a ton of cash and/or to stroke their own egos.
Boy ain't that the truth. I personally have known several individuals who have not just started their own organizations within an existing system, but have claimed to have started their very own system. Let me describe three of these individuals.
1.
The totally delusional clown: With a fairly low rank (Nidan?) in a Korean system, he "invented" his own system and began advertising to attract students. His skills were poor to mediocre at best, and my green belts could out-spar him. He did manage to keep a few students, such as his fiancee and his elderly mother. Eventually, he disappeared from the local scene.
2.
The enterprising egotist: He was my Si-Hing ("elder brother") in the Wing Chun system I was studying at that time and was an assistant instructor at our school (probably about equal to a senior brown-belt). Our school closed, so he took one short seminar with another Kung Fu master, then decided to start his own system. He had good sparring skills and was big, athletic, cocky and had a huge ego as well. Once he crashed my class wanting to spar. Anyway he eventually disappeared only to turn up as the featured master on the cover of a recent issue of
Black Belt Magazine. I really don't know what his skills are since I haven't seen him in about 25 years. He may be very good and making a bundle. I did check out his resume on his website however, and the only part of his training that I did know about (at our old WC school) was grossly inflated.
3.
The humble individualist: This guy was once a Wing Tsun student of mine, and a fellow FMA student under a well known master. He's also a long time boxer and has trained with many reputable people in a variety of systems. About a dozen years ago (having at that point some twenty years experience in the MA) he began teaching his own system of FMA. He felt this was the only fair thing to do, since he trained under various people and used a synthesis of all their teachings. Also this is common in the FMAs. Many of the current masters present their own systems after having trained with various other people. I asked this man why he went it alone, and he replied that, in part
he did it out of respect for all his teachers, since each had contributed something of value. And, since he has altered his teaching significantly, he feels it only fair to call it by his name, but
always giving credit where credit is due. Incidently, he is very good and although "mature" in years, can really lay it down.
Well, IMHO, as you pointed out, most who start their own style are like individuals 1 and 2 profiled above. On the other hand, if you find somebody like instructor no. 3, you just might want to train with him. That's what I chose to do.