Where is your proof that studies were serious in the 1960s? What does this make current studies? I've talked with folks who did studies and programs then and don't recall nobody claiming a higher seriousness to their studies then.

Viewgraphs or PPT it still is a "paper" study and it is no more or less serious then than now.

You can claim causation for anything you like this doesn't make it so. You need to show the direct link either by someone's written statement or some historical documentation of some sort. It simply doesn't exist for your idea that as we see more of Mars we be less interested in sending humans to Mars. This isn't even how people think let along a logical probability. If being "Moon like" is a turn off for Mars what must being "Moon" do to the Moon's attractiveness?