Why is Netflix deleting mega famous anime series?

I don't understand why Netflix is suddenly deleting a lot of famous animes…

Because they only bought the licenses for a certain period of time and did not / could not extend them ¯ \ _ (ツ) _ / ¯

Probably because the license has expired and you are therefore no longer allowed to offer it.

Ah!

Perhaps there are legal reasons or the production company wants more money.

Thank you.

Because the licenses have expired.

There are several license periods that can be purchased. For example, TV channels buy a 7-day license for their media libraries. I would say Netflix will buy for 2-3 years. (But it can also be different) Then you have to buy it again or take it offline.
There's no such thing as a "forever" license.

Now it is the case that most anime series already have their streaming services in Germany and Netflix is only buying a sub-license. So a sub-license to be able to offer the series as well. The actual main rights remain with the other service. If they say Netflix now they are not allowed to extend, then Netflix is unlucky. The other anime streaming services that have their say.
That's why Netflix often doesn't offer all seasons in Germany, because the old seasons are no longer so important for the other streaming services. New seasons are important to get others to subscribe to them. That's why you don't sell them to Netflix, just the old, unimportant ones.

The only thing Netflix can do to have sole rights to the series is to go faster and buy exclusive rights from Japan. That's how business works. First come first serve.

Series that didn't go down well, but of course Netflix won't extend them anyway and won't even inquire about them.

I think it's perfectly okay for series to go away. Because I don't always want to see the same thing and so Netflix has more money for new licenses instead of just spending the money on old ones.
If I just want to see the same thing over and over again, then I watch ProSieben.