The insider trading argument was proven to be nonsense. He had a <$5000 interest in a mutual fund that fractionally owns the drug manufacturer . For multi-millionaire to care about this would be like dumpster diving for pennies.
If anything the drug magically curing coronavirus would make the entire stock market, and his re-election chances, go up dramatically, so there is no need to look for an insider trading argument when plain old wishful thinking/stupidity explains it all.