"The highlights of his waning administration include encounters with Rudy Giuliani, a healthcare disaster and a dildo collector."
This sentence is meant to list certain "highlights" of Trump's waning administration. It give three examples: 1) an encounter with Rudy Giuliani 2) a healthcare disaster and 3) a dildo collector.
But when we name someone in an article, it's not unusual that we might give our readers a brief explanation of who that person is. Example: "I had the great privilege of interviewing Dr. Jane Goodall, a leading primatologist and climate activist." - This is not a sentence about 3 different individuals. After the comma is an explanation, not a list.
Similarly, after Rudy Giuliani is named, what follows could be read as an explanation of who he is. Without the Oxford comma, which would go just before "...and a dildo collector", the sentence could be read as indicating that Rudy Giuliani is the main highlight of Trump's waning administration, with a helpful explanation that Rudy Giuliani is both a healthcare disaster and a dildo collector.
The inclusion of the Oxford comma removes this ambiguity.