Not divine revelation SG.
Mores change slowly.
New ideas require time to take hold.
It is crazy to imagine everyone's position changing on the same day.

There was very little opposition to allowing SS couples civil partnerships.
It was a new arrangement so no preconceptions of it.
In fact it is exactly the same as marriage.

Aa thousand years of preconceptions about what "marriage" constitutes takes time to overcome.
Intolerance cuts two ways.