Lawmakers should have been more careful about which mergers and purchases they approved.
The Lawmakers in question are not involved in the actual approval process. They create the rules, but sadly don't do the full rule making[1] nor do they administer the rules. So, this is their check on what the executive branch has done.
1) its amazing how many laws are passed with the actual rules determined by departments in the executive branch. That's why it is so important to look at the announcements in the federal register.