CFIUS was set up by Congress to keep Congress and politics out of the process.
And by placing the Treasury Department in charge,
they apparently wanted to keep national security concerns out of the process as well.
"I am one of those who do not believe that a national debt is a national blessing, but rather a curse to a republic; inasmuch as it is calculated to raise around the administration a moneyed aristocracy dangerous to the liberties of the country."-- President Andrew Jackson - (1824)