If you look at the Old Testament the mediators between God and men were angels. I’m pretty sure it’s referencing thier role in the Old Testament before jesus was born and the holy spirit was given to the general assembly of believers. Sort of there was a time till this happened when angels mediated everything
“And it shall come to pass afterward, that I will pour out my spirit upon all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions: and also upon the servants and upon the handmaids in those days will I pour out my spirit.”
Joel 2:28-29 KJV
He was promising a new covenant that was personal to each one
“And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.”
Jeremiah 31:34 KJV
He was promising to give his spirit to believers eventually in that new covenant but until then you had angels as messengers and mediators ministering the covenant to man like this
“ his ministers a flame of fire “
“And the angel of the LORD appeared unto him in a flame of fire out of the midst of a bush: and he looked, and, behold, the bush burned with fire, and the bush was not consumed. And when the LORD saw that he turned aside to see, God called unto him out of the midst of the bush, and said, Moses, Moses. And he said, Here am I.”
Exodus 3:2, 4 KJV
or this
“Behold, I send an Angel before thee, to keep thee in the way, and to bring thee into the place which I have prepared. Beware of him, and obey his voice, provoke him not; for he will not pardon your transgressions: for my name is in him.”
Exodus 23:20-21 KJV
“And when forty years were expired, there appeared to him in the wilderness of mount Sina an angel of the Lord in a flame of fire in a bush.”
Acts 7:30
In the ot angels were often ministers of zgods messages and authority on earth . In the nt , you’ll bite it’s the apostles and other men filled with his spirit that excercise the authority and do the ministering of his message and words to the people