They reference CMB / CMBR for one main reason (spoiler): Wanda is creating a universe. That's it. They're just trying to hint at that before it becomes explicit.

That's it. That's the post.

I find the marvel universe exhausting. I tried to keep up for a while. It's nice that a Jack Kirby spread can finally be translated to the screen, I guess, but that endlessly tangled soap opera was purpose-built half a century ago to get you to buy more and more comic books with your allowance each week, and now that they want my leisure time as much as my dimes, I just can't afford it anymore.