@Hot Sauce
Tagging onto market research, I think one of their biggest failings is not having a compatible family of guns (sub compact, compact, full-size, XL) like Glock, S&W, H&K, SIG et al have. People like being able to share holsters and mags. Walther's "family" has always been quite limited; you could get a P99 and P99C, but not a full-size P99. You can get a large combination of compact and fullsizes with the PPQ and PDP, but no subcompact.
It's an obvious failure in their lineup...they're needlessly shooting themselves in the foot when they're already disadvantaged to begin with given Glock's market share. The only thing I can imagine is poor market research, I can't think of any technical reason that would keep them from producing a full lineup of PPQ/PDP pistols.
I think that's a failing Glock has with their 43 series that limits their success....albeit a smaller degree since they were a late market entry and the P365 came out so quickly after the 43, which sort of changed the game. All the same though, I remember quite a bit of sourness about the 43 and 43X/48 not have mag compatibility, and I'm positive that impacted sales in a negative way even though I can't quantify it.