People do all sorts of things when faced with a situation they don't feel equipped to cope with, are shocked by, panicked by, scared about...
Ignore, march on... laugh... cry... jibber about and get in the way... take over even if they have no clue...
Honestly it all happens and what you'd do in a situation with a fairly 'take charge' person shoving you out the way before you've time to think is not reflective of what you'd do in any other situation either.
I've panicked - old chap tripped and fell in the road, I was 4th on scene though 1 was absolutely rat-arsed, 2 jibbered and got in the way and 3 was my best mate who is very capable and at the time worked with the elderly... she took charge, I got a grip of myself and followed instruction and got rid of 1 and 2 who were not helping - we got him in the recovery position, my new teatowels under his head and called an ambulance.
I've zoomed straight in too - a lass at a bus stop we were walking towards (same friend as above), on an otherwise empty, going dark, drizzly street - she just dropped, folded like she'd been deflated.... by the time we got to her (a minute) she was fitting. Moved stuff to keep her safe, jacket under her head, looked in her bag/purse to see if she had any ID/medical stuff (couldn't get close enough to check neck/wrist for tags/medical jewellery. Called the ambo, stayed with her whilst she came round and was VERY confused and told her what had happened until the ambo came.
I'll bet that I was only confident second time round as I WAS with competent friend though, and because it was bloody obvious we were 'it'... there was no one else.
Sometimes too the most useful thing you can do is get out of the way - if others are dealing with things, too many people is just a pain!