Answer:
The reason behind Irish-German immigration to Pennsylvania in the 19th century and their inclusion to its industrial mills and factories was:
Religious tolerance.
Step-by-step explanation:
When Pennsylvania was founded, it was done under the ideas of William Penn and his religious tolerance beliefs. Due to the influence of the Quakers and their ideals. I attracted Swedish and Dutch immigrants in the beginning, but in the 18th and 19th centuries the ideas attracted German and Irish immigrants that believed the colony had the perfect environment to find new hope.