play into someone's hands
US /pleɪ ˈɪntu ˈsʌmwʌnz hændz/
UK /pleɪ ˈɪntu ˈsʌmwʌnz hændz/

1.
jemandem in die Hände spielen
to do exactly what your opponent wants you to do, so that they gain an advantage over you
:
•
By arguing with him, you're just playing into his hands.
Indem du mit ihm streitest, spielst du ihm nur in die Hände.
•
The opposition's mistakes played right into the government's hands.
Die Fehler der Opposition spielten der Regierung direkt in die Hände.