sorry, just ammending my spelling
A far smaller margin than the EU referendum which was hotly and sometimes violently disputed for years.
But as usual you conveniently miss the point.
If the old referendum rules had applied you would have needed over 50 % of the "Available votes". In simple terms if there were 1000 people eligible to vote the people wanting the change would have to number 501 at the ballot box. If 400 voted yes and 200 people didn't vote then the yes vote would lose. So there would not have been a welsh assembly nor Brexit.
In the figures you quote we have the Labour party now governing the county with a mandate from about 12% of the population. If there was a vote to scrap the assembly what do you think the vote result might be?