Because they knew they could do more and they would work because they knew they were getting money
Doc 1. 1917 was a time during war. The US did enter during this time, and also the Industrial revolution was still going. With tenements going up everywhere and factories producing needed products. Many families were poor at the time of this. There were workers needed. And who else than the relatively recently freed blacks (Pardon) as cheap labor for factories. Besides, the south had an unbelievable amount of racism still. The journey up north should've been very freeing.
Doc 2. Remember this was a time when there was still racism. Jim crow laws. The KKK (Klu Klux Klan) black people wanted out and now. There were lynchings. Set massacres. To find work elsewhere other than the literal (Pardon my french) hellhole in the south. To go up north was like heading to the promised land.
Hope this helps. (Now my head hurts from reading, Jk.)
A democracy works under meeting and exercise the government in person, while a republic is the meeting and agreements of the citizens. They assemble and administrate to keep the discussion civil.
They were all products of Enlightenment philosophies.
