British thing I believe, at least I've never heard it mentioned Stateside, though Wodehouse isn't very famous here. I think a lot of people were angry at him at the time is happened and stayed mad for the rest of his life.

It's further in the article:

It was largely innocent stuff...[but]...[h]is timing could not have been worse. June 1941 was a low point in the Allies’ conduct of the war. The Nazis, with tank divisions storming across Soviet Russia, seemed on the brink of victory. Wodehouse’s “treachery” became the object of hysterical warmongering in the British media, led by an alliance of the Daily Mirror and the BBC.

Honestly it rarely comes up as anything but a historical footnote in modern times. But back then... it was a huge deal.

> The broadcasts seemed entirely innocuous to me.

Well, the point was that he did them at all.