A decline in quantity of base capture is indicative of how preoccupied players have become with base capture
That's a very far-fetched interpretation in my opinion. The last big drop in the rate of base captures, for example was simply caused by HTC makign them more difficult. The moments the new, larger towns were introduced, the number of captures dropped.
Not the players changed - the rules did.
But what the chart shows that the players of AH1 were capturing a mighty lot of bases for not caring about base captures at all.
I will not disagree that player motivations, game culture have changed and have some effects... but they are smaller than apparently perceived.
And the war had always played a big role in AH 1&2, bases had been grabbed by hordes or sneaked, fields had been shut down, CVs were sunk, and there was much ado about it on the BBS.
Even back in the golden days.