Well, my guess is they aren’t going to support a website with whom 99.99% of their users probably find reprehensible.
What I do see here is an assumption of a political agenda based on what may not even be an exhaustive list of Scroll's list of publisher sites, likely based on a single graphic on their frontpage which contains 12 logos, of which four companies were mentioned here. Their about page[0] shows 24. Are all of these "leftist" outlets? Is their only relevant commonality left-wing political ideology?
Show me some evidence of non-crazy non-leftist publishers being rejected by this partnership due to their ideology and I'll agree it's odd. Until then it just looks like confirmation bias to me.
There’s a clear bias and, honestly, trying to pretend it’s not there is doing a disservice.
Whether that’s because Scroll is not interested in serving right-wing customers or because right-wing outlets are not interested in participating in Scroll, that’s going to remain a mystery I guess.
How is Fatherly[0] a "literally leftist outlet?"
The fact that so many of them are Gizmodo sites only tells me that Gizmodo joined the platform and all of the others came as a package deal. That's not furthering an agenda, it's good business, given Gizmodo's popularity.