Cabinet nominee should be allowed to have congressional hearings prior to being fully vetted by the ethics committee because many of these committee operations are nothing but shams and full of political posturing. When it comes down to it ethics and government do not go hand-in-hand. It is like watching sausage be made.
If they waited for all of the ethics committees to vet every candidate to their satisfaction, they would have a way to filibuster any candidate that they didn't like. Chances are, who got through the vetting process and who didn't would be a political decision. The President has a right to choose his nominees.
Every other administration for four decades has recognized the value of doing due diligence reviews of potential ethical issues and has happily submitted the names of nominees ahead of time. It avoids embarrassment and wasting of Congressional time if it turns out that a nominee cannot be confirmed due to unmanageable conflicts. US people have get to pay for all the time Congress will waste on confirmation hearings for people who may end up not being eligible to serve at all. In terms of 'draining the swamp' you all seem to be surprisingly okay with major Wall Street swamp monsters becoming part of this administration. It's almost as though your moral indignation at political corruption was just a cover to justify supporting Trump for less honorable reasons.
The vetting by the ethics committee should happen first. This would be beneficial for the hearings so that all of the imformation about a nominee is on the table and known. These hearings are very important to ensure that the right people are put into the job and to make sure that we don't have someone who is unethical or not knowledgable about their position.