It used to be that merely being a Protestant was enough to not want to help out the Pope. Especially when an organization states that they believe the gospel and seek the glory of God.
https://www.crossway.org/statement-of-faith/
"Redemption is wholly by the blood of Christ, and salvation is by grace alone through faith alone in our Lord Jesus Christ."
https://www.crossway.org/history/
"Crossway’s goal is to continue seeking the glory of God in everything we do—to proclaim his truth in power; to reflect his glory in content and design; and to express something of his holiness and grace to a fallen world."
Some people are going to be upset that a ministry (I use the word loosely of course) that purports to be about advancing the gospel and the glory of God is helping out Romanists.
I'm not sure why it is a shock that some are really against those who "trouble you and want to pervert the gospel of Christ" (Galatians 1:7) ... "if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed" (Galatians 1:8).
Whether they are right or wrong about the idea that Crossway is doing business with the Pope, is a different matter. But at the very least, it is, to me, an understandable reaction.
So, in a way, Crossway is going against its historical mission. They are breaking an implicit promise to Protestantism. Hence the feeling of being betrayed. I get it.