Looking at the offerings available for purchase, I disagree that there is a "huge market' for da/sa handguns. If there were, there would be a lot more to choose from. Retailers don't carry what doesn't sell.
You may be right about the XDE's destiny to fail. When I bought mine, it was glaringly obvious that it was as heavy empty as the M&P 2.0 was loaded. I disagree with your assessment of the trigger. Comparing it to other da/sa guns, I'd say it was on par. It was never going to compete with a sa or striker gun. I think that's just the nature of the da/sa design.
There actually is a huge DA/SA following. CZ, Beretta, HK, Sigs, FN, Springfield, Ruger, Taurus, S&W, Bersa, and a plethora of Turkey imports and imports from other countries have DA/SA offerings. Are they as popular as striker fired handguns? No, but there is a huge following still. I see it on other forums and in real life more so than on this particular forum.
While many gun owners may own and purchase more striker fired pistols, they still like and own DA/SA handguns too. It's not an either or thing. I also have more striker fired polymer handguns, but I still love and buy 1911, revolvers, and DA/SA handguns. Just like striker fired handguns sell much more than revolvers and there aren't many companies who manufacturer revolvers; however, revolvers are still very popular millions are sold each year in the U.S. I'd say there are more offerings of DA/SA handguns from various manufacturers vs revolvers and 1911s.
I've seen multiple threads several pages long on Glocktalk, ARFcom, DefendiveCarry, AKFiles, and several other popular gun forums where the members were also very found of DA/SA handguns. In these threads, there is usually always one or two members who are critical of DA/SA handguns, and would ask why would anyone choose those over Glocks and the like. They always get overwhelming pushback from just about all other members.
As far as the the trigger being on par with some of the other DA/SA handguns on the market, I agree. With that said, most of the other handguns on the market have built up a following, have excellent aftermarket support, and they have been in the DA/SA game for a long while. There is aftermarket support to enhance the triggers. SA execution of the XDe is the only reason why it failed. The main complaints I seen and heard from those who actually purchased one was it was a huge gun for what it was, it was very unattractive, the trigger was bad, the capacity was too low, and/or they still have a stick up their behinds over SA past political dealings. If those issues didn't exist, there is no doubt in my mind that the XDE would sell well. If Glock, S&W, Beretta, CZ, Sig, HK, etc would have made that same gun with the same features but without any of the cons, the gun would have had sold very well. If Walther, HK, or Sig made one that had the capacity of a hybrid 9mm, I'd buy one in a heartbeat as would many others.