30% doesn't seem anywhere near as low as it should be though... I'd say that qualifies as "so many".

That said I question both your and grandparents choice to look at only people who chose to vote. 68% of people who could have voted against this did not - either actively supporting it with a vote or deciding that they didn't give a fuck if it happened by not voting. Every potential voter either knew or ought to have known the result of this election result...