Well, I'll be honest and I haven't read the whole thread but what I can see is that there aren't as many breeders who are able or want to breed and run their horses.
Many of the breeders now breed for the sales ring. They want beautiful horses that will sell as yearlings. Many of the distance horses, just don't look great as a yearling. They mature later. That isn't good for those who are breeding to sell as yearlings.
In the old days, there were families who could afford to design their own bloodlines after many many years of careful study. They bred horses and then ran them under their own colors. They had vested interest in making sure that they were breeding quality that would last.
In this day and age, how many of the good three year olds run at four? Not many. If they were there for the Triple Crown and did well, into the breeding shed they go.
Many trainers can keep the horses patched together for a short campaign over two years. We've done great things with medical advances and such that the horses don't really need to be that confirmationally great.
What I see is that there are many horses that are being bred that have no reason to be bred. That is what is creating the breakdowns etc. Yes, freak accidents can happen but the fact is that the thoroughbred industry isn't breeding as much quality as they used to.
Feet are one great example. TB's don't have to have bad feet but many do. We could breed it out of the breed if it became important. Think about it, how many horses lost shoes this Triple Crown? One even lost it going to the paddock!
Do you ever remember that happening before? I've watched the Triple Crown for almost 30 years. This was the worst for lost shoes that I can remember.