There are a lot of conflicting rumours about Wonder Woman’s upcoming solo movie, but it’s widely believed that like Captain America: The First Avenger, the majority of it will take place in a period setting. World War I is the most popular theory right now, but regardless of when exactly it takes place, the character clearly has a long history in the DC Extended Universe.
Apparently, in Batman v Superman, Lex Luthor is well aware of that and a big part of his obsession with meta-humans revolves around the fact that he’s gathered photos of a woman – Diana Prince – who hasn’t aged for decades.
Before The Avengers was released, Marvel had an entire slate of movies to flesh out their world. The DCEU on the other hand is jumping straight into Justice League after this movie, so anything which provides some background is obviously going to be advantageous.
With Wonder Woman also set for a 2017 release, it’s essential that Warner Bros. get moviegoers interested in her story in advance (particularly because a female led superhero movie is still considered a risk), while Lex having knowledge of her existence will obviously help him come across as very smart and formidable.