Eh, I mean, the plot does make sense though if you just look at the core of it.

A perfect man does everything he can, but has his relationship fall apart due to a manipulative spouse that doesn't love him conspiring against him with infidelity until psychological turmoil causes him to commit suicide.

The part of it I'm assuming you mean when you say it doesn't make sense is probably Lisa being a huge bitch for no reason (as it's pretty commonly cited). That has no given explanation except that it was probably written by a person who went through such an event in their lives and just concluded that some women are just like that. It was even semi-autobiographical as it drew many events from Wiseau's own life.

I might be off-base though. What other part might you say doesn't make sense?