Someone coined the phrase “charismatic megafauna” back around the 1990s, IIRC. It just refers to large animals that humans like, and will therefore be more inclined to help in their rescue or conservation, e.g., elephants, whales.
I don’t think it has any actual scientific meaning, so it is very strange that it is used here.
Funny thing is that this particular “Charismatic megafauna” is from an epoch when humans would love them a lot...for DINNER! hahaha