Final answer:
Radical Republicans wanted to impeach President Andrew Johnson primarily due to his opposition to their Reconstruction policies and his violation of the Tenure of Office Act. Johnson's reluctance to redistribute Southern lands and his damaging public statements further fueled their motivations, aiming to shift power towards Congress and facilitate a more radical Reconstruction.
Step-by-step explanation:
The primary reason Radical Republicans sought to impeach President Andrew Johnson was due to a series of constitutional and political conflicts that arose during the period of Reconstruction after the Civil War. Johnson's opposition to the Radical Republicans' Reconstruction policies, including the protection of newly freed former slaves and the punishment of the former Confederate states, created a significant rift between the Presidency and Congress.
The breaking point came with Johnson's violation of the Tenure of Office Act when he attempted to remove Secretary of War Edwin Stanton, a Radical ally, without Senate approval. This act, alongside Johnson's confrontational speeches that damaged his reputation and the perception that he was lenient to the former Confederate states, fuelled the Radical Republicans' motivation to impeach him. Moreover, Johnson's policies regarding the non-confiscation of Southern lands showed his reluctance to alter the Southern social order, which was in stark contrast with the Radical Republicans' goals of upending the plantation system and empowering freedmen through land redistribution. The impeachment was seen as an opportunity for the Radical Republicans to strengthen Congressional power over the Presidency and continue their program for a more thorough Reconstruction.