Original: He was aided by the support of the Bavarian People's Party (BVP), which switched its support from Marx, and the refusal of the Communist Party of Germany (KPD) to withdraw its candidate, Ernst Thälmann.
Simplified: He was helped when the Bavarian People's Party (BVP), switched its support from Marx, the SPD candidate and the Communist Party of Germany (KPD) to did not withdraw its candidate, Ernst Thälmann.