John O'Sullivan at National Review looks into what could have motivated Vigano:
The Catholic Church serves, to a significant degree, as the lens through which the secularized West views Christianity in general. Dismissing this situation as less important than "climate change" or "protecting migrants" is tantamount to the Church, broadly speaking, saying to the world, "Even we don't take our own doctrine seriously, so don't worry about it. Whatever tattered remnants of what we've always called the Bride of Christ still exist are yours for the picking. You may find among them some useful tools in your social-justice machinations."
That's where the Devil finds his entry point.