Not sure how the federal post-employment COI rules work, but at the state you're forbidden from working in a position where you interact with your former public employer for at least a year, and usually 2 if you were at a decision-making or senior level. And you're forbidden forever from working for a private contractor on a project that you worked on or (especially) managed/approved a contract for while with the state.

At the state level, that doesn't prevent you from working for $BIG_CONSULTANT which got a lot of work from you before, but there has to be a credible firewall preventing you from getting assignments related directly to your governmental decisions affecting the company. Violations can be costly, and if proven in certain ways can lead to jail time. Do similar limits exist, and are they enforced, on the federal side? Something fishy may be going on with the fed rules if people can jump without obvious constraints from high decision-making public positions directly into a company that got significant benefit from those decisions.