Here's my take on it:

Compare the photos of Crooks here:

https://www.dailymail.co.uk/news/article-13752085/Photos-Trump-shooter-Thomas-Matthew-Crooks-raise-questions-assassination-attempt.html

with the photos of Yearick and the dead body here:

https://media.greatawakening.win/post/uNIhmpsGgkKB.png

Pay close attention to the hair color. Crooks has blonde hair and Yearick has auburn/brown hair.

This was an op, pure and simple. They had Crooks and Yearick wearing the same clothing. Crooks was the patsy who wandered around like an idiot so that he'd be noticed by all of the rally attendees. They were seeding the narrative with his image. They were expecting Yearick to make the shot, which he was fully capable of doing. He'd have assassinated Trump if not for the fact that Trump turned his head at the last second.

They had figured that once Trump was killed, that in the ensuing chaos they'd get Yearick out of there and blame it all on Crooks. No one expected the local sniper on the ground to actually hit Yearick on the roof, but when the local sniper did make the shot and hit the rifle and Yearick by extension, only then did the sniper on the roof take his shot. This threw off the original plan (of capturing the "shooter" (Crooks) alive?) and required them to quickly manufacture a story that explained everything.

To me, the autopsy seems to be a blending of narratives. Crooks, being tall and thin, doesn't seem to fit the description of the body being "well-developed," but it would describe Yearick. Note, also the description of the hair color:

"The body is accompanied by a clear plastic bag containing medium length brown hair (submitted as evidence)." Brown, not blonde hair.

Having to manufacture a new narrative would also explain why the body was cremated before anyone else had a chance to view it. They couldn't risk anyone realizing that the body was Yearick and not Crooks.