I don’t understand where you get this. The OT had priests. Furthermore they each had their official duties according to their orders much like the CC. Here is an explanation of the duties of the different orders (courses according to the jews).
**
The Duties of the Priests**
"Before the break of the day, the priests on duty were ready and they assembled to cast lots to decide the assignment of the various daily tasks. It started with filling the lavers and preparing the altar. At about 9:00 am, they opened the gates and blew the silver trumpets to announce the commencement of the morning service. The service included slaying the sacrificial lamb, salting the sacrifice, trimming the lampstand, burning the incense, presenting the burnt offering and drink offering, blessing the people and blasting the silver trumpets. This was followed by the Psalm of the day, presented by the singers, accompanied by instrumental music.
Immediately after the morning service, the Israelites might bring in their private sacrifices and offerings. It would occasionally continued till near the time for the evening sacrifice, which was about 2:30 pm. The evening service was similar to the morning service. It ended at about 4:00 pm.
At night, the priests kept watch about the innermost places of the Temple, including the inner court and the Temple itself. They also opened and closed all the inner gates.
On a Sabbath day, there were the weekly renewal of the showbread and an additional burnt offering of two lambs.
Before the Temple was built, David received instructions from the Holy Spirit and showed Solomon how to divide the
priests and the
Levites and how they were to serve. In the Temple, there were
several classes of Levites:
Priests (1 Chronicles 24:1-19)
Priests’ Assistants (1 Chronicles 23:4,28)
Singers (1 Chronicles 25:7-31)
Musicians (1 Chronicles 23:5)
Gatekeepers (1 Chronicles 26:1-19)
The priests and the Levites were divided into 24 courses within their assigned class. The length of each course was 7 days (1 Chronicles 9:25). The week of service began and ended on the Sabbath (2 Chronicles 23:8). In addition, all the priests served for 3 extra weeks during the year (Deuteronomy 16:16)."
www3.telus.net/public/kstam/en/temple/details/priest_service.htm
Notice how the Levites were classified into different groups each with their specific duty. We know that this was going on even until Jesus’ time because of Saint John the baptist’s father the priest Zechariah. He was called to his duty in the temple before John was conceived and this was after the destruction of the Temple by the Babylonians centuries earlier; so they kept the priesthood until 70AD.
My question is why was the priesthood in Judaism foregone with the destruction of the Temple in 70AD? And is this related to Christianity somehow?