If a women claims a man raped her should he be instantly arrested if there is no proof?

Someone close to me was accused of attempted rape there was no proof except the girls word. Since rape is obviously a horrible and serious crime he was arrested right away awaiting trial.

Her story was a complete lie and she just wanted to destroy his life and luckily this was proven in court and he was proven innocent and even sued her for emotional damage and won. $25,000 which is nothing compared to what he went through.

But back to my question he did spend about 3 months in jail for a crime he didn’t commit. I understand it’s complicated and had someone actually committed this crime you would want him off the streets immediately. But if there is no proof should someone immediately be thrown in jail for rape accusations or should there need to be proof first?

Edit- he was given two option one was to sue for money or press criminal charges had he pressed charges she would of received probation (nothing compared to the 3 months he did) so he chose to sue for money the $25,000. So had he chose criminal charges do you believe there should be more then just probation on her and false accusations should get a bigger punishment? This is a case of 2 minors so I’m not sure if it would be different for adults.

This case was also a clear case of false accusations she was filmed (without her knowledge) admitting that she made everything up to ruin his life.