It makes sense if you realize that there's no certainty a sale will go through and you don't want to pause all operations with the blind hope that a sale will happen
Having said that, if someone just joined before the sale and is laid off, they should get a generous layoff package similar to longer term employees since they may have just quit a job to go there and are now back on the market.
Ironically, German law says that the first six months are a trial period for both sides, and you can be fired during that time with a two week notice for no reason.
I don't know about German law, but in Finnish law you can only appeal to the trial period if you have an acceptable reason related to the trial period. For example, if the employee isn't performing well, that is a legal reason to annul the work agreement during the trial period. But selling the business to investors or having financial difficulties because of the economy are not acceptable reasons, since they are not related to the specific recently-hired employee.
It cuts both ways: the employee can walk out during the trial period for reasons such as feeling like they didn't fit in, or the work being different from what they imagined. But if they merely find a better-paying job elsewhere, they cannot invoke the trial period but have to give notice in the usual way.
Germany mandates two weeks' notice while person is on probation period, which is usually first 6 months. I haven't heard details about layoff package, but given sentiment I am not sure that it was great.
Having said that, if someone just joined before the sale and is laid off, they should get a generous layoff package similar to longer term employees since they may have just quit a job to go there and are now back on the market.