From that standpoint, Hemingway’s argument seems quite solid. Before September, 2019, Rudy Giuliani had been working in Ukraine to pressure the government to give up information that he could use to make Joe Biden look corrupt. This wasn’t a secret. He was boasting about it in the New York Times. (“There’s nothing illegal about it. Somebody could say it’s improper,” he told the Times — on the record!) Giuliani’s partners in Ukraine were widely suspected to be linked to Russian intelligence.
But all this was just another Trump scandal sitting in plain sight, mostly deprived of oxygen by all the other Trump scandals. Trump and Giuliani probably understood that the potential for their work to scuff up Biden was much greater than its potential to harm them, for the simple reason that there was only so much incremental damage yet another Trump scandal could do, whereas Biden had a pretty clean image that could be seriously tarnished if they got the mainstream media to treat their allegations seriously.
But impeachment created a five-month-long national tutorial in Trump’s plans to force Ukraine to help his campaign. It even got large numbers of Republican officials to concede that his scheme to use his presidential authority to conscript Ukraine into his opposition research operations was bad (even if none of them save Mitt Romney thought it was bad enough to remove him from office.)