Why is the Sacrament of First Communion before the Sacrament of Confirmation?

it was traditional for a bit of maturity to be had when confirmed, many now have both at the same ceremony . but the vatican is looking at confirming before the eucharist , so watch this space

It is not in the rite I grew up in.

Confirmation occurred with Baptism

Penance and Holy Communion were together as well.

In the western church:

quote

"According to the ancient practice maintained in the Roman liturgy, an adult is not to be baptized unless he receives confirmation immediately afterward, provided no serious obstacles exist."[8] Administration of the two sacraments, one immediately after the other, to adults is normally done by the bishop of the diocese (generally at the Easter Vigil, since "the baptism of adults, at least of those who have completed their fourteenth year, is to be referred to the Bishop, so that he himself may confer it if he judges this appropriate"

/quote

In the Eastern church, confirmation is done by the priest at baptism (whether of infants or adults)

You get first communion when you join the Catholic Church, then after a time, you get confirmed as a last step

Because the Catholic Church decided it should be, not because the Bible says so.