It’s a bit more complex than this though. Left-leaning/progressive Turks are more likely to be integrated in German society, gain citizenship or even give up Turkish citizenship. Whereas conservative/nationalistic Turks are more likely to be interested in Turkish affairs and vote in Turkish elections. So it’s not purely “expats are more rightwing”, it’s more that those expats who bother/are eligible to vote in their country of origin tend to be more nationalistic.