If every Democrat had shown up, Johnson would have held the vote open for hours until enough Republicans showed up to outvote them. Which would have happened, because Massie was the only Republican to vote for the measure.

But even if by some fluke the vote had passed, we'd be in a much -worse- position, because the impeachment trial would be managed by Republicans and go before the Republican-majority Senate at a time when no one is paying attention. They'd just kill it like they did the Trump impeachments. Much better to wait until the new Congress next year so we can have a proper trial run by the new Democratic majority.

from what I'm reading they had a 2 day notice about when the vote would be. But on the other hand, Johnson cut off the vote early as they were trapped in traffic.

So really it was a bipartisan effort, to fail.