the first century Israel society was a duplicative one. there were those who clung with the tenets of traditional jewish life; the dress, the feasts, torah reading, etc.
There were also others who were drawn to allurement of the contemporary greek Culture. They may still celebrate the three primary feasts, (Pesach/Passover, Shavaot/Pentecost, Succoth/Tabernacles) but didn't necessarily subscribe to the more conservative jewish daily life.
The Greek (Hellenistic) society was riddled with things questionable to a more moderate Hebrew; men wrestled naked, people waxed on a philosophically-based paradigm (versus a Theo-centric one), therefore, the more traditional Jew viewed the Hellenist Jew as secular and only jewish by blood, but not by practice.
This led to natural disdain towards the hellenist as seen in the Biblical Book of Acts chapter 6.
Hellenists were Jewish people who embraced Greek culture and customs, particularly during the Hellenistic period after the conquests of Alexander the great. They were influenced by Greek philosophy, language, and lifestyle, leading to a blending of Greek and Jewish traditions.