First of all, this differs a lot per country. The US being one of the worst here, where the EU countries are one of the best.
In nearly all piracy cases, it ends up with a financial consequence and rarely jail. Intentions matter a lot here.
In the pure case of piracy, you want to spread out paid content for free, this generaly is illegal. But in the artistic case, you use content of others to make something new. And here fair use is a common thing. Still, there can be a financial consequence as a result of it. But do also note, that even if you used exclusively content from 1 studio to make such PMV, that studio will still not become the owner of that PMV. It can however be made part of the deal to handle the financial part (and with good PMVs it isnt too unlikely to actualy even happen).
Only when you ask money for your PMV, you reach a domain in which you can end up in jail. And even then it mostly happens based on your behaviour.
Jail is rarely a solution in a civil case. Governments dont want to put someone in jail because some sort of company found 1 person costing that company a $5000 loss. A week of jail is already more expensive than that.
And dont forget that the US companies inflate the losses massively. In the EU they are far more realistic at estimating these things (if the company does use such inflated value, they actualy will lose the case by giving false information). This means that not every upload you caused with your PMV would have caused a person to pay for the content, and for PMV’s, its generaly the artwork of the PMV itself that matters a lot as they generaly ignore the pacing and artistic aspects of the original video. Its very likely that even if a pmv was downloaded 1000 times, that it wouldnt even have caused 1 sale on the original platform.
The last thing is also, the heavier a company acts against these things, the more they disrupt their own market. The company logos in those PMVs are a marketing aspect. Who says you costed the company money?
The only real exception is when someone is realy trying to maximize the money gain out of piracy. But in that case you enter the real criminal domain. And PMVs arent even remotely close to this. PMVs are still considered a work of art, and making art is not a form of crime even if that artwork technicaly could not exist without piracy.