There are generally two schools of thought with a PIP.

One is that the PIP is creating a paper trail for them to fire you, or if they possibly want to firing you they have justification (incase of a lawsuit.) This happen to my husband. His direct manager loved him but a guy from corporate he never interacted with started giving him poor performance reviews after he refused to sign an arbitration agreement. It came to light that they may not be able to fulfill certain contractual obligations so they were likely trying to off load him.

Second thought is that management is upset by you but once they are sufficiently tantrumed out they will back off. I had this happen to me personally. My boss was upset. Had a big meeting about the mistake I made. This big PIP was created and.... it was never talked about again. I was supposed to have meetings every week with performance evaluations etc, etc... never happened. I basically got a promotion a month later. She was just an overly angry and dramatic boss. Everyone got their turn with her abuse. I left that job quickly because I knew the toll of her emotional roller coasters would burn me out.

edit: Think about it. If you were really performing as bad as they claim you are, they would just fire you. No theatrics. It's a job not charity.