Sorry this is late, but this is what I came up with...
The Industrial Revolution needed a LOT of raw materials, so they needed to colonize. When they colonized, they would push their cultures on their new conquered lands due to their culture being "superior". They would also get cheap labor when they colonized. So, they needed raw materials and people to harvest those materials and colonizing gave them both, plus they got their empire expanded.
Hope this helped! :)
