The funny thing, if we take the entire period with Gygax and Williams, and just say they were both only there to syphon off money...and that TSR was on the edge of bankruptcy and then Williams got there just to siphon off money (that wasn't there)...it turns into an interesting debacle where we have to wonder, how do you squeeze money from a rock??
TSR was highly successful, both under Gygax and Williams. It got into trouble near the end of each of their time at TSR, and that led to an eventual take over by someone else (or sale) and a new edition eventually.
I think Gygax's time led to the game have sales equivalent of close to 100 Million (in todays' dollars, not back then), and Williams also had a high point where it was at 92 million in sales one year, and over 100 million the next (gross, not net, though that still would be close to or over 200 million in today's money).
I'd call that EXTREMELY good success for both of them. Of course, hanging in the background at the time, for both of them, was the mistakes that were ongoing (even driving the seeming illusion of such success as the gross profits above) that were giving an illusion of success, but eroding the foundation even as the roof seemed to be ever rising higher.
Both cases led to a quick and rapid demise in a very short time period, in consideration of the high's that they just had.
That said, D&D has always had this problem to a degree. If you can play with just the PHB, DMG, and MM, that's a one time purchase. How do you continue to make that money after those sales are done?
It's like this past year and past quarter. I expect sales for WotC are doing well, and would have been extremely surprised if they had not been considering that they just released core books and the things they were doing with MtG.
That's not what concerns me. It's what happens next? They have the same problem as D&D always has. How do you keep up the sales after the core books?
They accomplished the unbelievable and 5e just kept on getting bigger and bigger! I don't think that will happen with the anniversary edition (but, I'm willing to be happily surprised). I think they may have a problem. I'm hoping the new Box Set will sell well and make up for any decreases in the next coming quarters, but after that...I don't know.
If I had to bet, I'd say they will start work on a new edition in the next year or two (if they haven't started already, the pattern from the past is pretty clear, every time they've released a revised version of the D&D that came before it...it is around that time they should start looking at starting on the next version...with the only plausible exception to that being 2e IMO...of course).
So, it's just the pattern of D&D hit both of them, though I think Gary realized it at the end (though a little to late for him) and was trying to do something about it.
That said, loved TSR when it was up and running in the 70s, 80s, and 90s. It wasn't just D&D, it was the boardgames and other RPGs. I love Star Frontiers. I even love Lorraine's Buck Rogers....and love the Buck Rogers Board Game!
People hate on her far too much. I get it to a degree (I'm always a Gygax Loyalist...at least thus far), but I think she did some pretty good things and she shouldn't be maligned as much as she is.