I guess the author is mentioning public funding to try to make a political point, but it does not fit the narrative, because publicly funded research is the norm worldwide.

The glaring difference in how the US approached R&D is rather the way in which they manage to integrate the private sector, manage to convert research into products and manage to get funded for these rather risky private projects.

Also, with regards to why researchers flocked to the US, post-WWII, it was for the same reason that other people were flocking to the US (and Canada, and Australia): the new world had good economic prospects.