I'm gonna tell you like this.
1. If you get put on a PIP, that is the company's nice way of telling you to start looking elsewhere while you are still on payroll. I have worked in management for a few years and have seen a number of employees put on PIPs. I have only seen 1 work out and it was literally on some 1 in a million circumstances shiit.
2. PIPs are not just handed out like candy. There is usually a long process to get an employee on one. There will be multiple people and multiple step ups in leadership involved to clear it. There are a lot of checks and balances to go through. Managers essentially have to present mounds of evidence to get one approved. So more than likely, your cousin deserved it. Nobody really gets put on a PIP by mistake or because their manager wants to get rid of them for no reason...
That is why it's so hard to fire people. Companies would rather eat the loss of having a shytty employee, than face a lawsuit for an unlawful/unjustified termination