The factors were less economic possibility and overpopulation in the homeland.
Explanation:
The Greeks were rarely in favor of leaving their motherland for a foreign land but had to do it multiple time sin the history.
This was because of overpopulation at home which made less resources available for the Greek state and they pushed people out.
Often the people were exiled and asked to settle different lands in the time of such problems so as to keep the population of the mother state as low and as functional as possible.
The Greeks mostly settled regions in Asia minor.
