5th you have a lot of explaining to do. I am not convinced you are so naive. Your initial argument does not stand up to your faux naivete, given the very specific athletes you cherry picked for this topic. The truth is clearly evident and self explanatory, not to mention the many other athletes that have not had let downs (not fall offs) since trials.
It is a widely known fact that the US trials is the single hardest championship meet in the world. There is not a deeper country, nor another country with the ability to produce medallists from no where. I chuckle when people criticize the three past the post format. There is no other way to chose our team. For example, who knew Barbara Pierre was ready to roll? Who knew Queen and Nia were ready? No system is perfect but when competition is deep and fast , the best solution is between the lines. Yes, that can create some heart breaking results, but until the IAAF starts auto qualifying the best of the best, this is what will happen.
Let me take a look at your list you asked for causes, I will give it a shot:
Michael Tinsley - Been consistent all season. Nothing shocking about a bad race here or there, especially in the 400h. It is safe to assume he is training and traveling in preparation for Moscow.
English Gardner - She won her first race. Ran with the world number 1 for half of her first DL race and faded late. I do not see the problem here. 11.32 off the plane, first trip to Europe, 11.13 against the big dogs in her second race. New coach, training, and prepping for Moscow. Not to mention she had conference, regionals, ncaa, and US nationals all in about 6 weeks. Oh and she won every one of those meets.
Kimberlyn Duncan - Fresh off her collegiate season. A surprise US title with a windy sub 22. I would bet money her body is in shock, and mentally she is recharging.
Issiah Young - He needs to take a mental break. Someone get him a snickers. He ran a full collegiate season. A lot of sprinting in his legs. Refer to my detailing of all EG, it applies to all the collegiates. Lots of sprinting at a high level for them.
Bershawn Jackson - ???? What are we looking at here? The fluctuations of the men's 4h hurdles is pretty much uniform.
Natasha Hastings - Definitely recharging. She put all she had into winning. I expect her to be right and ready for Moscow.
I hope this helps and prevents you from trolling in the future. None is the above is mysterious nor insider information. Just basics of US track and field