Jesus is the High Priest because He intercedes on our behalf & offered Himself up for us .Because He was the perfect sacrifice, there was no need for any more sacrifices. Because He lives forever, there was no need for another high priest to replace Him. So, He is the forever King & High Priest. He also was the Perfect Sacrifice, that put an end to all insufficient animal sacrifices. That is why He could say on the cross, “It is finished.” He finished what the priests started & accomplished completely what they could only accomplish temporarily.