AFAIR, it was the "Grid Pro" and "Dashboard" features that were needed, but they were out of budget for our infant phase of the product and we went with React. It was a long time ago anyway, I last worked with Vaadin 7. I will however say, that I really enjoyed working with it at that time.

If you used React back then, what do you miss from the Vaadin world and what was easier in React in comparison ?

Have you tried one of the latest versions?

Disclaimer: I work for Vaadin.