I'll bet Trump misspoke when he first declared the opioid crisis...
...a "national emergency"
Knowing how he has a tendency to run his mouth off-script, I believe he accidentally said something that ran afoul of big pharm donors. Declaring the situation a national emergency would have freed up access to billions of dollars in fed help to go after this base for republican campaign funding. I don't think he knew what the words "national emergency" actually meant.
In a mad rush to cover for yet another example of the president's ignorance of how words matter, I think his admin cobbled together a carefully crafted XO that amended his statement to a "national health emergency", a subtle change that guts federal money for the problem.
It's not hard the believe that this is just another example of how Trump is a loose verbal cannon in a job he's frightfully unsuited for. I don't think he was supposed to say anything about a national emergency. The big question is what's next?