[justin66]

> Why can't it unfold etc in Earth orbit, where a repair mission can be sent if needed, and then travel to its Lagrange point?

Another comment mentioned that it's not designed to accelerate while it's fully deployed, and that's true enough. You'd wreck it.

The other essential thing is that there's no way to give it and its instruments anything like their designed operating parameters (pretty hot on one side of the sunshade, something like 40 kelvin on the other side) in Earth orbit.