President truman stated that the world was facing aserious threat of communism (socialism) which was eating up the most European countries.
It should be noted that socialism began in USSR( Russia) as a means of making properties and private owned properties to be owned by the community inorder to reduce the wide gap between the rich and the poor.
The most obvious reason is that one has to pack up and go because things are not so good at home. Long ago, that probably meant that the climate had changed and made life impossible. It might have become too hot or too cold or too wet, which in turn would have affected not only quality of life but also make survival a shaky proposition. Drought, flood, and temperature changes could certainly push people to move on.
I hope that helped a little.
Answer:
Because according to different family the needs of different family differ from each other