Could you explain sentence structures of these two to me?

Hi, teachers!

I'm reading an article in 'The Economist',

which is about relations between China and America around coronavirus.

1.

Yet what candidate Mr Trump said in 2016 and what America's president says are different matters. China has responded angrily to his administration's slurs. Where recent pandemics-including the 2014 west African Ebola outbreak-saw productive Sino-American co-operation, this one has take the already-poor relations between Mr Trump and Xi Jinping to new lows.

I hardly understand the meaning of the last sentence(bold)!

Does this mean 'before Trump administration, relations between China and the U.S. had been improving

especially in the areas where their co-operation was needed. But after power changed in the U.S.,

their relations became poor and appear to be poorer due to the coronavirus situation.'?

('Although' is elliptical before 'where recent pandemics...')

Is my understanding right?

2.

The best way to lower the tension would be if Mr Trump's diversionary tactic failed.

I don't know the structure of this sentence!

It's a much different sentence using subjunctive mood from what I've learned in textbooks.

Can I rewrite the sentence like

'If Mr Trump's diversionary tactic failed, that would be the best way to lower the tension'?

Thank you for reading my question!