For me, the best explanation of Mencken’s work was that he wanted to be like Friedrich Nietzsche. Mencken imitated Nietzsche’s basic concepts (despite differences on minutia). Here are the basics:

• Nietzsche was an elitist, and an outspoken opponent of any belief in God, organized religion, populist politics and Democracy — a system in which inferior men dominate their superiors. Mencken was 100% behind that thinking.
• Nietzsche suggested that War is good because it’s fresh air — it honestly faces the basic facts of life, namely, violence and death. When peacetime goes on too long, a nation becomes like an old maid. Mencken was 100% behind that thinking.
• Nietzsche was an atheist who publicly reviled organized religion — mainly Christianity — most especially Christian fundamentalism. Mencken was 100% behind that thinking, as shown by his famous coverage of the 1925 “Scopes Monkey Trial,” as he named it.
• Nietzsche claimed that a few strong men were born to rule the majority, who are weaklings. Every nation produces a few people of obvious superiority — an elite made by Nature — an Aristocracy made by Nature. Mencken was 100% behind that thinking.
• Nietzsche claimed that these superior men are regularly persecuted by their own nations, through systems like Democracy. Mencken was 100% behind that thinking.

Mencken read all of Nietzsche's works in the original German. Mencken was the first writer in English language to write a book about Nietzsche's works, i.e. The Philosophy of Friedrich Nietzsche (1907) Mencken was 27, and Nietzsche had just died seven years ago by then.