Simplify the following text for a Grade 7 native English-speaking person.
Original: Having made numerous controversial changes to the established stable of F1 circuits , Tilke secured the contracts to design many high-profile new world circuits from scratch , mainly in Asia but also in eastern Europe .
Simplified: Tilke made changes to many established F1 circuits . Because of this , Tilke was able to earn the contracts to design many of new new , high-profile circuits from scratch .