These Supremes are clearly singing a different song. For example...

Days between the district court ruling against Nixon and the Supreme Court arguments hearing an appeal: 49

Days between the district court ruling against Trump and the Supreme Court arguments hearing an appeal: 143

It's important to remember that the latter is rather par for the course. Typically, it takes around six months from the lower court decision before the Court hears the argument (three months to go through the briefing on whether the Court should grant cert, and at least three months of briefing after that before the argument is ready):

scotusblog.com - The certiorari process seeking supreme court review

Unlike U.S. v. Nixon, or even the Colorado 14A case, there's no government processes involved here. Nixon involved a Congressional subpoena; Colorado involves what the state will put on their primary ballots. This case is "just" a standard criminal prosecution - no government actions are being held up if normal order is observed. It's very common for criminal cases involving disputed questions of law and well-lawyered defendants to take a year or two to get to trial. If Trump weren't running for President, it wouldn't matter whether the Court moved quickly or slowly, and there would be no reason to expect that SCOTUS review would run any faster than normal. It's not entirely surprising - or even untoward - that the Court is following regular order. Or even rushing it a bit - I've seen a few Court observers note that it's unusual for a cert petition that was granted in (essentially) March would be heard in that term, since the briefing schedule has to be compressed in order to get the oral argument on the calendar by April.