1918 was before the Nazis...
1918 was just imperial German nobility (house Sachsen-Coburg aka. Windsor) vs. imperial German nobility (houses Hohenzollern and Habsburg) with the rest of Europe joining in for the fun of a good family feud (queen Vicky was emperor Willy's aunt)...
I wondered about that, too, but then I re-read it and I think the article means he asked, of WW1, “Who were the good guys in this war?”, to make the point that he didn't think the US should have been involved, and then, as a separate point, went on to say he couldn't understand why the US intervened in WW2, either.
That wasn't, of course, an unusual view in the US before the Japanese attack on Pearl Harbour in December 1942 (and, indeed, it was Germany who declared war on the US, not the other way round, in accordance with their treaty obligations to Japan under the
Tripartite Pact of 1941), promoted by Charles Lindbergh and an earlier incarnation of the
America First movement, which used the US experience of WW1 to argue that the US shouldn't get involved in yet another war between feuding European powers.
It was a very popular view at the time, and one I imagine was shared by Trump's father (indeed, given Fred's involvement with the KKK, I wonder if his name appears anywhere in the records of the
German American Bund).