40-yard dashes are not important for quarterbacks. But they still attract a lot of attention because they're the flashiest event at the NFL Scouting Combine. Marcus Mariota did very well, running a 4.52-second 40-yard dash, while Jameis Winston kind of flubbed it with a 4.97-second 40-yard dash. Again, this doesn't really matter: passing ability will determine the first pick. But it's high-profile.
So that's why this GIF of Marcus Mariota overlayed with Russell Wilson and Colin Kaepernick is fun. Because Mariota blows them away, too. From Niners Nation:
Being faster than two of the fastest quarterbacks out there is pretty good. Compare that with Jameis Winston's speed.
As I said before, this doesn't really matter. It's a nice bonus that Mariota's very, very fast and it'd surely be an asset in the NFL, but that's not why he'll be drafted high. That's because of his abilities as a passer. It's still pretty funny, though.