The square cube law. says an elephant just can't get that big.
The giant creatures seen in monster movies (e.g., Godzilla, King Kong, and Them!) are also unrealistic, given that their sheer size would force them to collapse.
If there were more oxygen in the air, I could see them getting twice as big as their current size, but the maths gets unworkable pretty quick as you get bigger.
That said, this may once have been a giant elephant sculpture.