The last time (and maybe the first time) most Americans heard of Volodymyr Zelensky, the Ukrainian president was at the center of a scandal that would lead to the impeachment of then-President Trump. Trump in 2019 threatened to hold up weapons deliveries to Ukraine — caught even then in a simmering war with Russian proxies — unless Zelensky helped him dig up political dirt on rival Joe Biden. Today, the shadow of that scandal lingers. How much did Trump’s toying with Ukraine, cozying up to Russian President Vladimir Putin and, ultimately, Trump’s acquittal on charges of abuse of power and...