Since no one wanted to actually answer this, I'll give it a shot. Likely a rhetorical question I know but again to make my point, I'll give it a shot.

1. Merneith. Bob Baffert had a positive for Dex. Luckily, he had a legitimate explanation for the postive test as his attorney told the media. From Bloodhorse.com:
[i]
"The groom that had Merneith had (COVID-19), and when he came back, he was treating a cough with Dayquil and Nyquil," Robertson said. "We believe that's how the horse came into contact with that substance because you would never give a cough suppressant to a horse. It's just another case of contamination."[/i]

2. Servis/Navarro/Rhien. From Bloodhorse.com
[i]
According to the indictment, Rhein further stated that, if anything, the SGF-1000 may appear on a post-race drug test as a false positive for a different substance "Dex." (While the indictment didn't offer further detail, people commonly refer to Dexamethasone as "Dex.") The indictment later says that same day Servis discussed Maximum Security's drug test with another veterinarian who agreed to falsify records to make it appear as if the racehorse had received "Dex."[/i]

My guess is that Oaklawn asked Diodoro for an autograph and gave him the $1000 fine to keep the betting public happy. Thank goodness he is back on track with getting up early and working harder than the rest of the folks on the backside.