I'd hardly say it's the death of the segment as the Deere garden tractors are obviously still made and still sell well enough that theres a 1-2 month lead time on them.
The garden tractor market downsized for sure with the introduction of more choices to the market.
SCUTs evolved from super garden tractors and certainty became a dominant force.
Z-turns were invented for commercial first then made their way into consumer hands for people who just wanted to mow and in a hurry.
As market share split the lesser quality builders stopped making machines they could no long sell. Leaving being Cub, Simplicity, Deere and a couple others still making a garden tractor that was worth the cost. Slowly that has dropped down to just Deere making a garden tractor that lives up to it's name and is worth buying. There simply isn't another company that has anything that can compete with the Deere x series riding mowers. Except for the X3 series.
I really don't think any company out there has the history or heritage to make a $13000 riding mower that anyone is really willing to buy. JD never sacrificed quality for price point, even with their box store machines you get what you pay for. Their is consumer trust in the brand that other manufacturers have lost along the way.
My x738 is in my opinion the best machine I could have gotten for my property. It does exactly what I want it to do every time I go to use it. I can push it as hard as it will go and it never breaks a sweat. It's worth every penny it cost.
Im really tired of people saying oh but a 1 series is the same money when set up the same. They aren't the same machine. Sure they do similar things but they are rather drastically different machines to use and operate. It's like saying crew cab pickup and a 4 door European sedan are the same thing. Well they cost the same amount of money. They both do the pretty much the same thing but the experience of each is drastically different.