T-Mobile is a subsidiary of  the German Telekom, of which around 1/3rd is owned by the  German state. Since they once where a 100% state owned entity there are certain restrictions they have to follow. One recent of them is that the German gov wanted them to give free internet to poor children/students. That was fast tracked due to corona and somewhat extended into foreign markets. So that free 100GB for yours is not from a greedy cooperation. Its from the German gov.