You're right we shouldn't go by one data-point.
In the past few years since Trump was elected we had the Blue Wave which was sold on having Trump held accountable during the Midterms, Nixon, the current impeachment probe, and multiple polls having a decent amount of interest in having Trump impeached.
Even Republicans were successful at making Hilary's email scandal a thing in the 2016 election based on nothing, but having an impeachment probe on Trump committing treason with Russia in plain sight isn't feasible for Democrats because reasons.
To be fair to Pelosi/Dems, they DID launch an impeachment inquiry based on Mueller report late July. That Corey hearing was an impeachment hearing. But they're also currently undergoing some court cases to try to not only get more information out of the Mueller Report but to get their witnesses too.
Then again I'm one who thinks they should've launched a year long impeachment inquiry like day 1 which encompasses the concentration camps/separation policies, Trump's racism, emoluments, Mueller, and everything else. I want the Dems to show that this is literally a crime spree, not just "Trump did x and x was illegal".
Plus the Ukraine stuff WILL be bouncing back to Mueller related stuff and already has I think. Manafort hangs like a shitty shadow over the entire thing. Not to mention that practically this same bribery/extortion happened in 2017 that literally changed the course of the Mueller investigation and very successfully obstructed him...