But the democrat appointed heads had all the power?
So a political appointee who wants to expand government finds willing allies.
An appointee who wants to reduce government finds opposition.
The association of individual political parties with those positions is more variable.
But this neglects the millions of contractors and other positions that are also funded by government spending, which is harder to measure, and does change more over time.
https://www.brookings.edu/articles/the-true-size-of-governme... (2020, but the article doesn't clarify if the 5m includes short-term census workers)