It's an election year remember? Let's ask Mitch Mcconnell about the procedure:
McConnell's reasoning at the time? It was important for the Senate to "give the people a voice in the filling of this vacancy" by waiting until the new president took office.
"The American people may well elect a president who decides to nominate Judge Garland for Senate consideration," he said. "The next president may also nominate someone very different. Either way, our view is this: Give the people a voice."
So that's that. We need to "give the people a voice" and wait until after the election.