Nickelback is one of the most hated bands in the World, so they know what it is like to have people criticize them. Because of that, they don’t want people to go after their fellow Canadian Ryan Reynolds and his movie Deadpool & Wolverine.
Therefore, they recorded a message to remind people how successful the Deadpool franchise is. And it is hard to argue against what they said.
But then again, they have an ulterior motive. They have a song in Deadpool & Wolverine, and the more people who see it, the more money they will make.