Back in the 1970s, most of the satellite imagery wasn't taken by NASA. It was taken by the National Reconnaissance Office (NRO), a then classified government agency. NRO images are typically classified at the SCI (Sensitive Compartmented Information) level, which is normally considered as greater than top secret. Once in a while, some of the images are downgraded to lower classifications like Secret, but normally that's only at a lower resolution that doesn't show what the satellite can really do. It isn't easy to get an SCI billet. It took several months and an extensive background investigation before I got mine. The idea that a part time NASA employee would have that kind of clearance is laughable.

Most of the non-NRO imagery was low resolution Earth resources stuff taken by Landsat. That imagery had a resolution of on the order of 50 meters or greater (depending on the sensor), meaning you couldn't see trees or even many buildings. The resolution was so low for a variety of reasons. First, there were bandwidth issues at the time that limited how much data you could transmit to a ground station. That, combined with the multispectral imagery, meant that you couldn't take high resolution images. They were more interested in covering a broad area than in getting high resolution. There were also political considerations - many nations didn't like the US taking these images in the first place because the information gleened from the images had economic repercussions (e.g. detecting crop failure).

Of course, none of this matters to the true believers.