IMO, presidencies can be usurped by ridiculous impeachments and also by a administrative bureaucracy which believes that the entrenched administrative state of 3 and 4 letter agencies should have more power in the government than does the Congress and the President.
"Can be" isn't the same as actually happened. The claim was: "the Democrats have a history of trying to take over the presidency though indictments and impeachments," and as far as I know (and I've been around a while now), that has never happened.
As to your specific charges, first, whether or not Trump's impeachments were "ridiculous" is debatable. Abusing Presidential authority by withholding military aid in order to have foreign governments investigate one's political opponents and obstructing the investigation by ordering members of his administration to ignore subpoenas are not ridiculous charges. Nor is the charge of inciting an insurrection. There is nothing ridiculous about these allegations and, if true, they would have serious implications, no matter who the individual was who committed them.
Granted, Trump was not removed from office for either impeachment, since there weren't enough guilty votes to clear the two-thirds required, but that doesn't make the charges ridiculous. The Senate didn't even view the evidence before voting so the vote doesn't seem to be based on the facts of the case, rather on politics alone.
But, I'm not sure exactly what you mean by the other charge, referring to the "entrenched administrative state of 3 and 4 letter agencies." Could you be more specific, and perhaps explain how that could constitute an attempt to "take over the presidency."
-- A2SG, though, I'm still unaware of any attempts by any agency, no matter how many letters in its name, having done anything remotely close to that.....