Kent State happened because the Left wanted to ramp things up to convince people that Vietnam was Nixon's War and not LBJ's War.
That was part of it. The desired results were achieved: to make 'the man" look like the oppressor, to malign the military (even at the National Guard level), and to provide martyrs for 'the movement'.
All provided visual impact 'evidence' for the various flavors of Communists of The New Left, and, ostensibly, reasons to rebel against traditional American Values.