I used CNN's own photos showing the supposedly "half-empty" area "during" the speech. CNN had an interactive drag view. I panned over to the chapel on the right and noted the clock tower showed almost an hour after the inauguration speech.
CNN used a photo taken after the event to show empty areas. Also, the apparent "proof" that it was live were the screens showing Trump speaking. However, they were all different and obviously on replay.
CNN's own website pictures of the inaug did that for me. Especially the clock proof.