To explain Giuliani's inept performance, a number of people have cited how long it has been since he has practiced as an attorney. The idea is that he was really smart when he was a U.S. Attorney 30-plus years ago. But, like some baseball player who hasn't swung at a pitch in decades, he's lost his coordination. (I think I've heard a half-dozen different people advance this notion.)
To me, that explanation seems just this side of nonsense.
Let's just stipulate that Giuliani was once pretty good at the legal biz. As I recall, he was something of a hot dog, but he must have had something going to be able to parlay his prowess into becoming Mayor of New York City.
Are we to think either that
1) practicing law -- as a prosecutor or otherwise -- would keep someone tuned up in ways that are required for dealing with the completely unique circumstance of advising and doing PR for a President of the United States like Donald Trump, embroiled in the situations he's now caught up in? Or
2) discontinuing the practice of law (but being engaged in such challenging activities as being Mayor of NYC and running for President) would mean that a person would lose the ability to think in a lawyerly way, or any other clear-thinking and strategic way, that would be needed for playing the role Giuliani is playing for Trump?
I don't see how either of those is plausibly the case.
Whatever is wrong with Giuliani -- whether he never had what it takes, or whether he's lost what he had (due to age-related cognitive decline or otherwise) -- I don't think it has anything to do with his not having been a practicing lawyer since the 1980s.