You need to catch up.
The use of the expression "clergy presiding at weddings" is INCORRECT.  It's not what the Church teaches.
The couple preside; they confect the sacrament.
Form and matter.
The form is the couple's vows.
The matter is the conjugal union.

The priest doesn't preside.

The priest is there as a formal witness for the Church that the vows were exchanged freely in union with the Church.  Unity/Communion.