Stephen Miller worked the DHS and HHS the way you described in the first Trump administration. Presumably Biden had ample time to “seize these levers” no?
Biden chose not to use the power available to him to its full extent. He could have done something really extreme with the immunity he was granted by SCOTUS, but instead, he disavowed it.
That's because people who are not power-hungry see the dangers in becoming too powerful (and therefore often best suited to be in power). Not saying Biden was the best president ever or anything, but power-hungry leaders for the most part do not work out well for citizens -- history is full of examples.
