How can people actually lie about rape?!?

So Use to have a friend, let's call her Maddy. After about half a year of actually being friends with her I realized she was super gross and annoying and obnoxious. Anyways we still had classes and still talk.

Long story short she lied about her ex boyfriend raping her! When she told me, I had no reason to not believe her but she told like EVERYONE. THEN A COUPLE MONTHS LATER SHE SHOWED ME MESSAGES BETWEEN HER AND HER EX AND SHE ADMITTED TO LYING. she didn't even say anything to me about it. She just showed me an entire convo they had and she admitting to it being rape was only a small portion of it so idk if she forget it was in there Orr???? NOW she broke up with her boyfriend and is now talking to her ex that she said raped her. HE ACTUALLY FORGAVE HER. THEYRE ABOUT TO DATE. AGAIN. so that's just fucked up but whatever. They can make their own choices and mistakes.

Now there's another girl in our school lying about a rape! Basically this girl fucked a kid. The kid didn't like her and ghosted her. She went mental and was crying. This other guy, lets call him tom, picked her up to hangout. They went back to his place to chill. She then shoved his hand down her pants and said she wanted to fuck tom. Tom was like no I don't want to cuz we r to close of friends (and she was still crying about the other kid that she already had sex with as this was happening)

So, a couple days later, tom told me about what Natalie(nat being the girl that tried to fuck tom) did and how he was super weirded out.

4 weeks later school started and people started asking Natalie about what happened with tom. (Some people knew cuz tom told another person who blabbed) Natalie made up the lie that she got raped, yet she hasn't gone to the police or anything and it's been like more than 2 months. So becuz she hasn't told anyone ( except every student in the school) and tom told me weeks before school and before she even made up the lie, she has got to be lying. Like why would tom of told me about it weeks before, when he didn't even know what Natalie was gonna do. Like he would of had to be super invested in that lie and tom would never do anything like that (I've known him for years).

Tom lost so many of his friends (friends he's had for YEARS) and people r giving him so much shit (although lots of people r also giving Natalie shit cuz they think she's lying).

The school found out and asked him and he said they were just rumors. The school was like ok then but if this gets to the police there's nothing we can do. How can people fucking lie about rape when it will ruin the persons life!???! Wtf!