I wonder how the decision process went.

Perhaps something along the lines: "Wow, look at that ugly page from Dropbox. My eyes hurt! Let's make ours even uglier!"

It's all about "Designer experience", not "User Experience" in this case (i.e. trying to be edgy for the sake of it, in order to impress your designer / PM peers)

Is this a joke? I visited the website on my phone and it's horrible broken with "cards" all over the place.

Their website UX is far worse than IBM Plex. How can it be?