Just take a drug legalization. Many Republicans have been vehemently opposed to it. Take a look at the Supreme Court decision Gonzalez v. Raich, where Steve Scalia no less, wrote that the feds could interfere with your growing some plants inside your own home for your own personal use.
Remember that the "states rights" movement started as a response to federal action to end segregation. In my personal opinion, Republicans are just for whatever will push their agenda forward, without regard to the moral or ethical depravity involved in doing so.
Democrats, in contrast, are a bit more principled (in my opinion), especially when it comes to protecting the human rights, civil rights, voting rights, and other rights of the non-dominant groups in this country.
The position on "closing down" (that it was up to states) doesn't tell us anything about the administration's principle in regard to COVID because the administration is willing to change those "principles" very quickly, as evidenced by their current statements (among other actions taken by Republicans)
It's arguable that the position on closing down was based on the desire of the admin that the country remain "open", but was faced with legal/political difficulties in directly applying their desire to the country as a whole. What ever tactic is taken with respect to this Pact, we should be unsurprised if it ignores any "principles" and instead looks to effect the policy that Trump desires to put into place, or the effect on Trump's perception of his authority.
For example, he knew that getting hold of medical supplies and PPE would be difficult, and that the federal government would fail at it, so he put it in the states' hands. He didn't want to be blamed for shutting down the economy and forcing people to isolate themselves, so he allowed the states to decide. But now he wants us to believe that the "heroic" decision to open things back up again will be his, and his alone.
It's way older and more sinister than that. States' rights was first used to justify the continuation and expansion of the institution of slavery.
https://en.wikipedia.org/wiki/Origins_of_the_American_Civil_...
States Rights was dug up before the Civil War as a continuation of that argument, this time in the context of slavery.
Ah right, I'd forgotten about that. IIRC "What can the federal government do?" was a key question that divided Jeffersonians and Federalists.