In the Early Church, it was predominantly adults who first became Christian and celebrated the sacraments of initiation (baptism/confirmation/eucharist). Nevertheless, infant baptism became the norm quite early in the church. But Baptism/Confirmation was still the form of that celebration.
In the West, Bishops retained the right to confer Confirmation while in the East, priests were delegated to continue to celebrate Baptism/Confirmation. In the West, at an appointed time the Bishop would come to celebrate Confirmation. After celebrating Confirmation, the newly Confirmed would receive their first communion as fully initiated members.
Pope Pius X in 1910 lowered the age for the reception of First Communion to the age of reason. The prerequisite for celebrating Communion was still Baptism/Confirmation. However, given the number of infant baptism far outpaced the number of Confirmations a Bishop could do, there was the unintended consequence of Communions taking place before Confirmations had been celebrated. In other words, more children reaching the age of reason and celebrating Communion in the parish before Confirmation when the Bishop visited. The normal order of the sacraments became disrupted and with it the narrative understanding and meaning of the sacraments of initiation.
In an effort to address this unintended consequence, Pope Pius X left it up to the local bishops to decide the age for Confirmation. In some dioceses, the original order of these sacraments has been preserved. If communion is celebrated around the age of reason, then Confirmation is also celebrated prior to the reception of Communion. If Confirmation is postponed to a later age, then communion is also postponed.
As part of the sweeping changes of Vatican II, the catechumenate (i.e. the Rite of Christian Initiation for Adults who are unbaptized and wish to become Catholic) was restored and with it the order of sacraments of initiation. But that is a somewhat recent event that still has some generations for this restoration to take full effect in the understanding of the faithful and more importantly in the practices where Confirmation is after communion for those baptized as infants.