Here's a bit from Müller in 2015:

"The arrival of a theologian like Benedict XVI in the chair of St. Peter was no doubt an exception," Müller replied. "But John XXIII was not a professional theologian. Pope Francis is also more pastoral and our mission at the Congregation for the Doctrine of the Faithis to provide the theological structure of a pontificate."

See some commentary on that here

https://www.commonwealmagazine.org/cardinal-müller-discovers-new-role-cdf-under-francis