One of the most distinctive features of Trump 2.0 has been the breakdown of the rule of law. The administration has routinely ignored the law and settled interpretation of existing law in a wide variety of domains.
It has enacted illegal tariffs, it has denied due process to immigrants, it has deported immigrants to countries to which they have no connection, it has illegally impounded Congressionally appropriated funds, it has conducted the Iran war without complying with the war powers act, it has illegally and in violation of international law bombed suspected drug boats in the Caribbean and the Pacific and killed survivors of its attacks, it has unlawfully meddled in state election processes, it has fired government officials whom Congressionally enacted statutes don't allow it to fire, it has pardoned January 6 insurrectionists, it has corruptly allowed officials to benefit personally in monetary terms from their offices, it has openly admitted to denying FEMA disaster relief based upon how states have voted in recent elections, it has brought sham criminal prosecutions of political opponents, and so on.
Trump 1.0 was odious, incompetent, dishonest, and violated some political norms and legal rules, but shows much less disregard for the rule of law and for well-established political and legal norms.
What changed? How will that affect future administrations?
A lot of the change can be fairly attributed to the courts, especially lower court judges appointed by Trump and the U.S. Supreme Court, which attained a conservative majority and an ultra-conservative plurality under Trump 1.0, consistently letting Trump circumvent rulings against him personally, and against his administration, made by lower courts and non-Trump appointed judges (including many judges appointed by Republican Presidents in prior administrations).
The U.S. Supreme Court's decisions to grant Trump expansively Presidential immunity from criminal liability for his official or arguably official acts (even if they are clearly ultra vires), and to interpret the insurrection clause out of the 14th Amendment, were some of the earliest and most damaging of its steps down this path.
Yes, the U.S. Supreme Court hasn't given Trump a complete blank check in Trump 2.0 to be a dictator, largely because the non-ultra conservative justices and the liberal justices on the Court has sometimes formed coalitions to block the ultra-conservative agenda. But this hasn't been consistent enough to discourage mischief in the executive branch.
Of course, the Republican controlled Congress also hasn't pro-actively intervened, but as some justices on the Supreme Court such as Gorsuch are starting to acknowledge, while Congress has significant power to deny funds to the President, Congress has very little capacity to pro-actively contradict or restrain a President inclined to ignore it.
The relative irrelevance of Congress has also been illustrated by Trump 2.0's heavy reliance on executive orders to act, rather than Congressional legislation, despite the fact that Republicans hold majorities in both the House and the Senate, and despite the fact that past precedents have pretty well established that the filibuster in the Senate is a voluntary restraint that the Republican Senate majority has afforded to the minority, and not a legally binding barrier to action, and despite the tight hold that Trump has acquired over the Republican party, effectively turning it into a MAGA party.
So, the existence of a GOP trifecta has, in practice, been less important to the disappearance of the rule of law than judicial and especially U.S. Supreme Court, connivance in facilitating unilateral illegal actions by President Trump (in a highly partisan fashion that it did not afford to President Biden).
Indeed, if anything, the Republican majorities in Congress have been more even handed in protecting the limited rights of the minority Democrats in Congress on a non-partisan basis, than SCOTUS has been in its rulings, many of which simply can't be explained by anything but partisan bias.