The US education market has always been huge, but it has also always been highly fragmented. That fragmentation made it largely unprofitable and not worth the attention of huge multinational corporations. When you consider trying to sell to 50 idiosyncratic states, each of which contains (on average) 300 school districts, and each of those mostly autonomous districts contains (on average) 380 schools broken up by student ages between elementary, middle and high schools, further divided by the demographics of various communities, you can see that it is not a coordinated market that can make billions for someone with a “one size fits all” product line.
“Education reform” has changed that. Pearson has been able to change that. “Common Core” has brought some predictability and uniformity to a chaotic marketplace. If you doubt that Common Core was wired for Pearson, this Politico investigation should disabuse you of that notion.