Del-ton is the victim of someone else making a better mouse trap.
Del-ton had a niche in the "entry level", "afforable" or "economic" (or however you wish to say it) market. They did well enough holding their own it for a while..but, they got beat.
PSA beat them at the game. Fact is, nobody can offer near top level quality at the prices PSA lists for. They built their business hardcore in the "volume" model, and may be one of the few firearms makers that ever has done so successfully, so far. What's different is...most companies that use that model, cuts corners in some way to keep profits. It's usually quality. But, that's not the case with PSA, and as a result, they are slowly killing the competition.
Windham was first, now Del-Ton. There will be others. It's getting hard to be a "stand out" or get marketing attention when your selling basically the exact same product as many others.
Face it, there are only so many ways an AR platform can be made, and still meet the Mil Spec standard. (Yes, I'm aware that doesn't mean military acceptance). PSA has just figured out the most efficient way to do it, and has the marketing talent, to sell enough volume to return a profit.
That's just Captialism, and it just works.