Why aren't these IG dismissals causing national scandals?
Simple answer: Because we're all too exhausted from prior scandals, and too damn busy and concerned with coronavirus.
https://www.lawfareblog.com/why-trumps-inspector-general-purge-not-national-scandal
--"Trump, in explaining Atkinson’s removal, made no secret that it came in response to Atkinson’s having gotten Trump in trouble.
--"'I thought he did a terrible job. Absolutely terrible,' Trump said over the weekend. 'He took a whistleblower report, which turned out to be a fake report—it was fake. It was totally wrong. It was about my conversation with the President of Ukraine. He took a fake report and he brought it to Congress, with an emergency. Okay? Not a big Trump fan—that, I can tell you.'
--"Nor did Atkinson himself doubt that the move was retaliatory. In a statement, he said that “[i]t is hard not to think that the President’s loss of confidence in me derives from my having faithfully discharged my legal obligations as an independent and impartial Inspector General, and from my commitment to continue to do so.'"
In other words: This is retaliation, plain and simple.
But! Sondland's & Vindman's previous dismissals 2 days after impeachment have already forced Trumpists into the position of considering any retaliation by Trump as all fine and dandy, because it technically "doesn't break the law."
So these Trump cultists (and at this point, it's not inappropriate to start using that word) will only turn against Trump if he's proven to be a lawbreaker. But that's not possible either, because sitting Presidents cannot be criminally indicted per OLC guidance, and Trump otherwise stonewalls investigations to the maximum extent possible (and the GOP Senate lets him).
Impeachment in this day and age is constitutional dead-letter. "Let the voters decide!" was the rallying-cry of many moderate GOP Senators voting against firsthand witnesses in the impeachment trial.
Indeed, only voters can decide if they want to put up with 4 more years of this.