Need to understand Republicans' ever-evolving (or -devolving) defenses of Trump criminality and abuses of power? The "Calvin & Hobbes" comic strip and MAD Magazine, among others, explain.
Calvinball -- the eponymous game invented by Calvin -- probably captures the defenses best: in Calvinball, no iteration of the game is the same as any previous iteration because "you make up the rules as you go." Moreover, "[r]ules cannot be used twice (except for the rule that rules cannot be used twice), and any plays made in one game may not be made again in any future games." Hence, a chaotic game. Thus, Republicans' defenses of Trump (and even Trump's defenses of Trump).
MAD Magazine's 43-Man Squamish (also here) complements Calvinball. While Calvinball's chaos-inducing rules are at least comprehensible, the rules of 43-man squamish aren't -- indeed, are obviously designed to make the game unplayable. Similarly, Republicans' defenses are constructed to make unworkable the constitutional mechanism of impeachment (or, for that matter, any constitutional mechanisms of presidential accountability).
The Gish gallop (also here, here, here, here, here, and here) should look instantly familiar to anyone who has tried to follow the flood of lies, deceptions, and diversions emanating from the Trump Maladministration and its too-numerous invertebrate Senators, Representatives, and apologists. The Gish gallop finds odious sidekicks in PRATT (i.e., point refuted a thousand times; cf. here), and in the "one single proof" fallacy. The Dunning-Kruger effect (also here) -- "[t]he psychological phenomenon of illusory superiority" -- and the Peter principle -- the notion that "people in a hierarchy tend to rise to their 'level of incompetence'" -- often play supporting roles.
So, if the Rs' efforts to defend the indefensible baffle you, that's the point. For me, MAD Magazine, Calvin & Hobbes, and the Gish gallop, along with the other phenomena mentioned above, capture and explain nearly all of the Rs' insanity. Perhaps they will for you, too.
N.B. At this point in American history, the "R" identifying politicians (e.g., "R-Ky.") surely no longer stands for "Republican" but instead stands for "Russian Asset."