Well of course its fun to speculate, but none of us were there so who knows what the bull was thinking.
From my armchair (youtube viewing) it seems that Cape Buffalo do occasionally come with obvious deliberation from some distance out.

But its the close ones that sort the men from the man-buns...

One of the best filmed close buff charges is here.
If you're impatient, fast-forward to the 4-minute mark and watch from there.
If that doesn't get you puckering, nothing will!

Can't believe the cameraman actually stepped into the open and remained steady as a rock.
Respect!