The executive summary is something like: there are various reasons why it's better to be close to L2 rather than to sit still at L2 all of the time. More sunlight (not in earth's shadow), better communications coverage, easier station-keeping, etc.
Once you offset from L2, earth's gravity "pulls" at an angle. That pull can be viewed as the vector sum of a component toward the sun and a component perpendicular to it.
The perpendicular component is the "pull" that keeps Webb in an orbit, just as though there were a real object at L2 to orbit around. (The toward-the-Sun component, of course, keeps Webb in an orbit around the Sun.)
Webb's orbit around L2 is very large; bigger than the moon's orbit around earth. It takes about 6 months to make the full trip around.
👍good stuff.. And thank you for the link.
Great link!