ZeesKite – “it is a Halacha. One must stand for someone doing a mitzva.”
If what you are saying is true, then the Rosh Yeshivas and Rabbonim would stand as well, and they don’t. There is no mitzva to stroll down an aisle. The mitzva is performed during the ceremony and the masader kiddushin explicitly excludes the audience from participation and that’s why they sit.