The ouroboros is an ancient symbol depicting a serpent or dragon eating its own tail, is often interpreted as a symbol for eternal cyclic.
So O.B., the only TVA member who remembers what happened during the course of hundreds of years (see how he remembers Mobius from 500 years prior to their present), O.B. who represents a circle without beginning nor end - in opposition to the protagonists that jump from present to past to future, in a straight line of events.
Tony regularly visited Bruce during the 5 years and Bruce kept bringing up him, Steve, and Natasha throughout the episode I’m gonna cry he misses them so much!