They often seek to create calamity and crisis - with Covid; spreading fear (of immigrants, etc.), hatred and violence; disrupting health, education, and housing; international peace and security (NATO, Ukraine, etc.). You never see them spreading calm and peace - crisis seems necessary to their movement.
Tanking the economy does the same thing, but it is a much bigger step that impacts many of their supporters. What is their exit plan?
I expect part of their plan is to blame others: They will blame Democrats somehow, and other political enemies - it doesn't need any basis because the Dems don't have any effective means of refuting it to the public; whatever the GOP says becomes reality. I suspect they'll use it to ramp up hatred and fear, blaming their current objects of hatred such as immigrants, minorities, certain religions (a traditional object of blame, the right has already been normalizing antisemitism and general prejudice - which makes antisemitism inevitable. Rogan recently hosted a conspiracy theorist blaming Jewish people for 9/11, for example - how long before does he blames them for the economy, 'undermining President Trump'), liberals, etc.
Edit: I did some rewording
Making America "stand on its own two feet" would give it a lot of freedom in making choices that are at odds with future super powerful China that is no longer benevolent.
In that context, a lot of it does not make sense. Why the threats about annexing Canada or Greenland? Why the tariffs and extremely hostile rhetoric towards all allies? If you are preparing for a war, the stupidest thing you could do is to alienate your allies and push them toward your adversary. China is already approaching the EU, and I am sure they are negotiating with other key players too. China even agreed on a joint response to the tariffs with Japan and South Korea. Let that sink in - China, together with Japan and South Korea!