Trump is claiming that China suppressed information about COVID - causing it to spread internationally - in order to damage the U.S. economy.

For the sake of argument I take the premise that the Chinese government will do whatever they think is in their best interest without regard for morality; does this argument make sense?

China and the U.S. aren't competitors as suppliers. Hurting U.S. manufacturing capability doesn't significantly increase their expected sales.

The U.S. is already playing catch-up in telecom standards. Letting the world see us scramble to get back into standards bodies does more damage to our reputation and leadership than anything pandemic related.

The U.S. is a large buyer, so decreased U.S. consumption hurts China in the short run, though not as much as those in favor of a trade war seem to think.

Net, I don't think hurting the U.S. helps China significantly.

The better argument for why they would want the virus to spread is similar to major online platforms supporting stricter regulation. (GDPR et al) Only the large orgs have the resources to comply, raising barriers to entry for smaller players. In the same way, if pandemic response introduces friction to international trade larger players are more able to respond, driving smaller players (eg: Viet Nam, Cambodia, etc.) out of business.

The downside is they didn't know enough, at least when the virus first started spreading, to predict what would happen. How deadly would it ultimately be? How long would it take to get it under control? Does infection prevent re-infection, leading to herd immunity?

Unless we believe that they actually did know the answers to these questions, it seems like a huge gamble to intentionally let it spread for the possible benefit of improved competitive position relative to smaller competitors once it's all over.

I'm sure there are conservative "think" tanks pumping out explanations of how China is responsible for ... something. Are any of them making any good arguments, or is it 100% ex post facto rationalization for the conclusion they started with?

China has economic competition. If China’s economy gets shut down and no one else’s does, that’s bad for China. All China has to do to prevent that is say nothing. Short term it looks bad. Long term it secures that vulnerable market share. Whether you believe it to be a bad idea or not is irrelevant. People do things that are bad ideas all the time but generally because they believe them to be in their best interest. Governments have done far worse for far less to gain. As mentioned above, many believe our own government has done the same. Are the Chinese incapable of making this sort of gambit?

We'll never get someone from the Chinese government publicly admitting to it, so the best we've got is speculation. His argument is that it makes sense for them to do it. I don't think so.