Unless things have changed...
generally...
Marines don’t salute while moving. Those Marines were moving. Not sure why.
Marines don’t salute indoors unless under arms. Those Marines are not under arms.
Marines don’t wear covers indoors unless they are on duty or under arms. Those Marines are on duty so they are wearing covers.
Exceptions? If Marines are under orders.
Yet, there are photos of stationary Marines saluting Pres. Trump indoors.
In looking at the actual video, i wonder what the event was and what was the protocol for that event ?
Maybe the Marines saluted when Pres. Biden entered and paused in the hallway then they moved into position.
Might be a good dig to find out the why the Marines apparently didn’t salute.
They had better, of course they do.
Marines don’t salute indoors unless under arms. Those Marines are not under arms. Marines don’t wear covers indoors unless they are on duty or under arms. Those Marines are on duty so they are wearing covers.
If a Marine is wearing a cover indoors, he salutes. He usually doesn't unless under arms, that's true. If he is covered he salutes. Marines are ALWAYS on duty if they are alive even in civvies. If you are covered for whatever reason you are saluting should the need arise. Part of the 11 General orders. Under arms also consists of the duty belt, hence the cover. This does present problems with other services' General. From experience.
We never hear the sound, if any, of those indoor salutes, as with Trump. As I recall there could be a third person, NCO maybe, calling cadence, and if a qualifying dignitary shows up there could be something like: Att-ten-shun——sa-—lute. We never get to see what’s around the corner?
I remember early in Trump's (first) term, he ordered that the Marines be armed, perhaps the first day.
Odinga and the Clintons disarmed them, out of disrespect, or fear, or whatever, doesn't matter.