Your interpretation is correct. It's an unusual choice of words. I believe Maugham is deliberately reversing "best-liked." "Best-liked" is so common that it is often spelled as a hyphenated compound word. The phrase "best-liked man" is familiar and carries a cloud of associations: someone so charming, so full of bonhomie, that everybody enjoys his company. By manufacturing the opposite, "best hated," he is drawing an analogy to "best-liked."
I've never tried to analyze it, but "best-liked" carries both the idea that people like him more (he's more charming than the second-best-liked man), and also that more people like him than they like anybody else. These two ideas are just muddled and mixed-up together.
If I'm right, the reason why Maugham uses "best" rather than "most" is that "best-liked" is the common, idiomatic phrase and "most-liked" isn't.
Reversing a phrase for humorous effect--even though it no longer makes logical sense--is a common form of wit. It depends on the listener recognizing what has been reversed. For example, the phrase "a winning personality" means a pleasant, engaging, friendly personality. If I wanted to describe someone who was socially awkward and repelled people, I might possibly say "he has um, what to say, a losing personality." "Losing personality" isn't a real phrase and doesn't make logical sense, but I would expect people to catch the idea that it is the reverse of the phrase "winning personality."