It's mainly funny, because all the women look bored out of their mind. It makes it look like they're letting Greg blather on, even though none of his points are novel to them. And Greg has such a massive ego that he doesn't notice no one is listening to him.
Obviously, yes, Greg probably is just a person without ego talking normally. But him being the only dude in the picture and the only one talking, the mansplaining interpretation is a little too close for comfort, which makes it funny.
Fuuuuck, they cover the walls of our science buildings with those now. It's like, how much are you spending on this shit, but you can't fix the fucking HVAC in the building?