Those who can, do.
Those who can't, teach.
It's the American Way. Well, maybe the Earth Way, I don't know. I know this though.... if you spend two months reading every trading book you can get your hands on and you have good graphics and literacy skills, and a good editor and publisher, you can write a book that has as good a chance of helping newbies to trade as anyone else. Which is to say, apparently about 10% to 20% depending on whose stats you accept. What I am saying is it is easier to write about trading and trading systems than to actually put them into practice and not allow the human element to pee in the punchbowl.
It would seem like the market is overcrowded but apparently demand for easy get rich quick schemes keeps the market healthy and active, always has, and always will. The secrets to success probably involve lots of bogus reviews on Amazon and I don't mean just a dozen, either, and good marketing and ad placement. I would START with about 30 glowing reviews, which should cost you probably $50/each if school is out. Throw one or two bad ones in there, and then some comment threads correcting those reviews and telling the reviewer what he did wrong. Then you need to shell out some bucks to google or their advertising middlemen, and this won't be cheap but it should pay off nicely. Don't try to get away with calling a 30 page booklet a book... man up and write out about 300 pages. For extra credit, double that, and call it The Big Book on Trading or the Bible on Trading, or the Encyclopedia of Trading or whatever similar titles you can come up with that aren't already taken and protected. The same high schoolers you will recruit for reviewers could maybe help with filler material to fatten up the book. You need the cover art to really grab the eye even in a small search engine or forum site ad. Fine detail that clutters up the cover would be counterproductive. Then do a "sequel", an ADVANCED book with basically the same material but possibly some shilling for sites or brokerages or software vendors, and a few additional strategies and indicators. With two books out, you are an author and you can offer courses and webinars and stuff. Don't forget the youtube videos that tease the viewer into clicking on the training links. A slick but simple logo would be good at this point.
Not saying at all that all authors are like that, and it doesn't matter anyway. Every book I have looked at on day trading presented usable knowledge, IMHO, and I think my trading book collection is just shy of 40 books. At least 3/4 of the books on day trading stocks would have singlehandedly taught me enough to get started. Sure, some are better than others, and I have a natural bias toward the first book on trading that I read cover to cover; it was good, with a great presentation, but no special tree shaking revelations that aren't in most of the other books out there. When you have read one, you have read them all, right? Well, not exactly, but when you have read three or four picked at random on Amazon, you nearly have, yeah.
So yeah, if you are pretty smart and experienced in small business or in writing professionally, go for it. Why not? It's not like you are ripping anyone off.
Uh, don't forget the disclaimers about how you can lose all your money and there is no guarantee that you will make a dime trading.
Obviously there are a lot of authors out there who have been successful at trading. Why do they write and teach, when they could be trading? I don't know. Altruism? I won't speculate. Me, I would never be able to find time to do both. No way Jose. I think I could make money doing either one, but I would rather not have to interact with idiots, so I would prefer trading. If you are a touchy feely unicorns and brotherhood people person, teach and write. If you are a grouchy grumpy kind of guy who can't be bothered to answer the phone or put on some drawers and answer the door when the doorbell rings, then trade. There are lots of books out there that will reveal all the secrets and make you successful at it. I think anybody on this forum COULD be a successful trader if he just WOULD do what must be done. Average intelligence, average mathematics, computer, and literacy skills, and STICKING TO A PRACTICAL PLAN would put most failed traders or failed traders to be somewhere in that lofty 20% who break even or better.