When thinking about the percentage of failures of different types of tires, it might also be useful to think in terms of how the trailers are used. I would suspect that a very large percentage of travel trailers only roll but a "few miles" each year. Many, if not most owners have a working life that means the trailer may only go camping several weekends a year, not far away, and perhaps one "big trip" a year of less than a couple of thousand miles.
Point being, when not used much, could well be a entry market level product like a inexpensive tire, might serve that user well.
The other side of that coin is that some of us pull a lot more than that and so we might consider our needs and expectations are higher.
This hobby is a lot like other hobbies ( motorcycling and boating are examples ) where many folks buy this stuff, and then end up not using it as much as they had hoped or wanted.