It was not that 'some greeks were buddhist" (an insignificant number might have been), but in that some buddhists in those areas were influenced by the ancient greeks / greek culture which arrived there with Alexander the Great.

So it's the other way around mostly. E.g. you can find statues of Buddha after that interaction that are clearly influenced by hellenic sculptures (in their look and aesthetics), but not the inverse (greek e.g. Apollo statues influenced by Buddhist statues).