IANAP, but this is precisely the question I tried to address in this post:
If any of this is wrong, as I said there, I’d be interested in understanding why. I think the “curvature of space” perspective isn’t particularly helpful, but the gravitational potential vs centrifugal force perspective seems to be compelling. This is all in reference to an elliptical halo orbit like the Webb’s which resembles an ordinary Keplerian orbit. Despite the absence of a mass at L2, the JWST is drawn there because it’s orbiting through an area of higher gravitational potential in the earth-sun system. This is similar to a weight on a string that describes an elliptical orbit because it’s drawn to the lower gravitational potential at its natural rest point, even though there’s nothing physically there.
ETA: I should add: the nature of L2 is that it’s the highest point of local gravitational potential along the sun-earth axis. It’s “downhill” on either side. But that’s not where JWST is orbiting. It’s orbit is more perpendicular to that axis. It’s downhill in the direction of its center at L2, just like in a Keplerian orbit around its barycenter.