It's 100% both sides. We haven't had a president work to roll back his own power, since ... Hmm. Maybe Gerald Ford? I guess Carter was fairly principled on some of this.
This part of the system - executive power grabs - is supposed to be curtailed by the courts first and congress second in the US system.
> We haven't had a president work to roll back his own power,
this is just not true. For example, all under the Obama administration
* the closure of Guantanamo Bay and other black sites, the prohibition of torture as an interrogation method including updates to Army Field Manual and mandatory access of Red Cross to any POW, all represented a significant reduction in executive power in how we treat detainees.
* following the Snowden leaks there were several actions taken to curtail executive power in applying surveillance programs to both US citizens and non-US persons. these also rolled back several components of the PATRIOT act (passed under his predecessor we all know and love, Dubya)
* the signing statements reform meant the executive no longer had an effective line-item veto
* the AG under Obama implemented a new DoJ policy limiting the use of "state secret" privilege during litigations.
I agree with those things but they were not rollbacks of executive power. That was Obama using executive power to reel in bad policy, not ceding the power entirely.
Of course perhaps he couldn’t. Congress needs to do that, and the courts, and neither seem interested in doing their job. Lower courts sometimes step up but the Supreme Court seems to be on the side of a dictatorial executive for some time now.
What does Congress even do these days? Seems like half crackpot debate club and half hospice care facility.
There are light years of space between the behavior we're seeing now and "a president working to roll back his own power," and even that has arguably happened in many presidencies, depending on what you mean. You would need much more than that to demonstrate anything approaching behavioral parity on this dimension. Otherwise - yes, politicians from every party, forever, everywhere, exhibit some similar faults.
This part of the system - executive power grabs - is supposed to be curtailed by the courts first and congress second in the US system.