Lots of smaller dishes get you resolution but not sensitivity. You can image the black hole at center of galaxy, but you can't detect the red-shifted radio waves from beginning on universe.
Also, doing interferometry is much harder when the telescopes are moving.
I get it, but even on terra firma, they are having to track relative to each other in 2 axis. In space, they would have to add that 3rd dimension and I stipulate that extra dimension is not linear in complexity. However, tracking on the ground in RA and Dec per object across the distances of VLA is not "simple".
Also, doing interferometry is much harder when the telescopes are moving.