xkcd

It’s a precedent because presidents take power–not use the power they were given

Bush was given several literal blank checks during his two terms in office by a legislature that was more than happy to invest enormous power in the chief executive (so long as that executive was a Republican). The Patriot Act, the No Child Left Behind Act, the Medicare Prescription Drug, Improvement, and Modernization Act of 2003, the Department of Homeland Security Appropriations Act, 2007, the Consumer Product Safety Improvement Act, and the Emergency Economic Stabilization Act of 2008 were all on the books before Obama took office.

They each invested the Presidency with new powers via the national bureaucracy, enormous slush funds through which to shape economic activity, and regulatory authorities only vaguely defined by the legislature that the President's appointees could fine tune as they saw fit.

In point of fact, Obama’s restraint did put constraints on Trump. It meant that he had to go to court multiple times over things

Trump's trips to court were notable only in so far as they illustrated how toothless the modern judiciary is in the face of a Unitary Executive. Policies that failed to pass judicial muster were continued in defiance of court orders and over the objection of administrative bureaucracies - border wall funding and illegal incarceration of asylum seekers, kick-backs to private security firms and Homeland Security contractors, wildly illegal misuse of military assets in Iraq and Afghanistan and Eastern Europe and Latin America, leaking state secrets to foreign nationals, harassing and spying on minority groups and political opponents, using federal money for self-enrichment and as kick-backs to cronies, using federal money for campaigning in defiance of campaign finance laws - all ended up either being swept under the rug or continued under the incoming Biden Administration.

Obama did nothing to restrain Trump. In fact, Trump's team deliberately pushed the boundaries of what was already generously afforded them just to see how other branches would respond. And the response was, more often than not, to ratify his actions after the fact - either at the national level or via state policies in red states that sympathized with him.