All 4 ancient Churches, the Catholic Church, the Eastern Orthodox Church, the Oriential Orthodox Church, and the Church of the East do not allow an ordained man to marry.
But they do allow a married man to be ordained.
So this goes back to at least the 4/5th centuries
The only way (theoretically) a man could marry after seminary is if he didn’t get ordained after seminary and waited to receive the Sacrament of Holy Orders until after he found a wife and married.
Or entered seminary AFTER getting married.
Seminary life (as it currently exists) would be very taxing on a marriage without having a totally different program for married men.