In the intervening time, a candidate not quite ticking all the boxes but with motivation and energy could have learned what they needed to and moved whatever the project is forward.
And for me it's clearly a people one.
It can be that the manager don't want to actually hire someone because they have personal interest of using consultants to do the job. Or the manager lack confidence and is looking for a unicorn to avoid making any mistake (probably the most common). Or the manager expectations are disconnected with the job proposal (they want a senior but the salary is for a junior or like said in another comment, they want someone with skills exactly aligned with the tech stack).
Here we have a trial period of at least three months so it's quite easy to get rid of someone if they don't fit but it's rarely used in IT and I don't understand why. And once the trial is over, it's quite hard to get rid of someone. But basically it seems that once your in, if the trial period is used as a quick exit it's mainly by the new employee and not by the company.
I agree. In Switzerland employment law is governed by the code des obligations, or for the parent poster who asked in the first place, Obligationenrecht. There are various notice periods, 1 week in the first 3 months, 1 month for the first year and so on. An employer isn't required to give a reason for dismissing someone either.
I think it is entirely a people issue.