I am the fool who tweaked Qt to work with long-distance X11. The main problem was slow startup; if the ping time to the display was 0.1s, then applications needed 0.5s or more to start. So I fixed that, tested it using Qt/X11 applications on a transatlantic link, then fixed whatever else that I noticed because of the slow link.
As far as I know, noone ever made use of this work.
That didn't prevent someone at Trolltech from trying some of the same again twelve years later, except this time with better buzzwords and more effort.
So why did I do it? I don't remember. Perhaps someone had told me that X11 was network-agnostic by design and Qt's implementation fell short of the design, and I let myself be persuaded. Perhaps I told myself. One thing is sure: Noone had told me that this was a problem for their actual, concrete, existing application.
Maybe my work helped sell a seat or two for Qt. Many people are willing to pay for features or performance they don't need, so it's entirely possible. But I think it was probably waste. I feel good about it, though, because quite recently I was able to avoid a mistake by having learned from those two.
I've been a professional programmer for twenty years now. That seems to be long enough that for whatever mistake anyone proposes to make, I have made or watched a similar mistake at least once before. I'm not sure whether that's good or bad. Seeing a mistake be repeated is such a sad feeling.