Re: I am taking command of the fleet.
Agreed that the fight from Typhon sector to Earth may well have taken days. But if so, there would probably also have been time for Starfleet to send in reinforcements, and to keep organizing the battle so that the constant losses would not pose a problem in leadership...
Picard would have exploited a brief opportunity rather than an inevitable and permanent collapse of the chain of command, then.
Since "First Contact" take after "Paradise Lost" could the Fleet HQ lack a lot of admirals after Hayes was killed?
I for one would not summon aggressive admirals in the capital after an attempted coup
"A person without any sense of shame is no longer a human being."
Mencius, Chinese Philosopher (c. 372-289 BCE)