Two big differences between the clinton impeachment and Trumps is first there was a special prosecutor doing the behind the scenes investigations. With Trumps DOJ now controlled by Barr who appears to be neck deep in this fiasco this is not an option which requires the democrats do the initial evidence finding in the house. Second the vote to start the process in the clinton impeachment was due to them needing to grant themselves the power to subpoena. The GOP in all their benghazi hyperventilating granted that power full time to committee heads so there is no need/reason to do that vote.