And the D's may have been a bit nervous. And the evidence may have been... questionable.
But this mess highlights the risks of election interference and lobbying. The US may have evidence of.. something. For me, the highly dubious parts of this 'Russian' interference circle back to the origins. So Manafort's company (along with Black and Stone) had been working in Ukraine on Yanukovych's election campaign, which is where Kilimnik came in as a Ukrainian fixer. Who may or may not have some remaining ties to Russia.
Meanwhile, the US had been working to make sure Yanukovych didn't win, and the State Department apparently wasn't happy about Manafort's meddling and support for a pro-Russian Ukrainian presidential candidate. So the US should have some evidence of these murky goings on, but may not want to highlight it because a) it's classified and b) shows US election interference in Ukraine on both sides of that election.. Which didn't happed due to the Maidan 'peaceful protests' and a lot of dead Ukrainians.. And that mess happened during the Obama/Biden/Clinton era.
But that shit-show left a bunch of pro/anti Russia Ukrainian oligarchs and politicians looking to secure power, influence and of course cash, which is where Biden made himself a tad vulnerable for stating he made US aid payments conditional on having a Ukrainian anti-corruption investigator fired so they'd stop looking at Burisma, who just happened to employ Biden's son. But a bunch of anti-Russian Ukrainians who'd happily smear Russia for their own gain. Or just attempt to influence the US election because the Democrats had put Ukrainian politicians in power.
So to me, this mess seems strongly centred around Ukraine, not Russia.. Especially wrt aspects like why Clinton/DNC servers may have ended up there.