Franz von Papen is also a member of the Catholic Center Party, but he is far more conservative than Brüning.
In fact, he's so conservative that he has no support from his own party — his only real support in the Reichstag is with the DNVP (Conservative German National People's Party).
This switch is part of Hindenburg's overall shift to the right. Hindenburgs' victory in last month's national elections was made possible only with votes from members of the Socialist and Catholic parties — too many conservatives and right-wing nationalists had voted for Adolf Hitler, who came in second.
This dependence on non-conservatives embarrasses Hindenburg, who believes he can make up for it by shifting to the right.
Adolf Hitler had expected to be Brüning's replacement, but he won't get this job until January 1933.