If there's one thing I've learned from reading the histories, listening to the podcast, and observing all of the RPG companies I knew in the 1990s crash and burn to various degrees, it's that from 1975 to roughly 2010, it was very, very hard, nigh impossible to run a successful RPG company. You'd have your big-selling game. There's demand for additional material, be that supplements or adventures, but every release that is not your game gets diminishing returns. You can get an influx of revenue from a new edition, but really it's just kicking the can down the road. Ideally, you'd like to have a wide variety of products, but RPGs are not mainstream enough for a company to support multiple games indefinitely. Then you overestimate the demand for a product and order too big a print run, and then you're in a hole you have to dig yourself out of. Then video games come out and reduce your market. Then CCGs come out and destroy your market. Then MMORPGs come out and dance on the ashes that are left.
Set aside TSR for the moment. Look at the other major publishers in the 1990s.
White Wolf - Merged with CCP in 2006, hasn't been independent since.
Iron Crown Enterprises - Filed bankruptcy in 2000.
Mayfair Games - Shut down in 1997.
FASA - Ceased operations in 2001.
Steve Jackson Games and Palladium Games seem to be the only ones still active from that era, in their original incarnation, and it seems like they did so by shrinking the RPG product lines to the bare minimum and relying on direct sales of print-on-demand and PDFs, as well as Kickstarter.
And I think both the move to PDF/Print-on-Demand products and Kickstarter are the reason we even still have an RPG industry today. The ability to a) identify exactly how big the market is for a product, and b) reduce printing costs is exactly what an RPG company needs to do to survive. But nobody had these in the 80s and 90s.
In retrospect, the 1980-81 fad was the worst thing to happen to TSR. It let them grow too big, too fast, and when the bubble popped, there was no way for them to recover. At least, no painless way. Gygax's LA profligancy and royalties absolutely did not help, nor was Williams' use of the Random House contract in anyway a solution. But, I think the bigger problem was that after about 1983, TSR was simply bigger than the RPG market could accomodate. Their only way out was eventual acquisition by a bigger company.