They would have no reason to mutiny against Picard. Again, context. A mutiny on a starship was so unusual that the Pegasus incident was near legend status. This is a crew with a new captain and a chain of command, not a seasoned crew willing to risk their career because they don't understand the orders being given.
And a captain isn't a higher rank than all other officers on the Enterprise at the time? Not sure the modifier "mere" is appropriate here, given that being a starship captain was considered rather prestigious, and being on the Enterprise-D prestigious still. It was not an assignment given to "mere officers."
Same goes with the captain.
Because there is no line. The captain gives an order, you do the opposite, guilty of mutiny. There is no reason for the crew to mutiny in the above scenario. There are multiple reasons that they actually would not based upon the time, their experience, and recent events in Starfleet history.
They mutinied against Pressman after learning he had developed an illegal cloaking device, thereby making him a criminal. Starfleet officers are only required to follow their superiors lawful orders. Once their superior is revealed to be a criminal, no order they issue can be considered lawful, therefore no officer is obligated to follow any order from them.
They are two different situations. AGT we're seeing the crew serving under a captain they know nothing about aside from the fact he's one of Starfleet's finest, so they follow him without question. In Allegiance they see a man they've known for three years acting completely out of character and have probably cause to suspect something else is going on here.
Then consider the Riker Factor. In Allegiance it was Riker who convinced everyone Fake Picard was dangerous and orchestrated the mutiny. Riker wasn't there in the season 1 segment of AGT, meaning there was no one to instigate a mutiny.
Indeed, not to mention the situations were different. In AGT they were going into a potentially lethal situation, same as any Starfleet mission. In Allegiance they were going into definitely lethal situation.
The other side is the fact that Picard is willing to tell past Yar that he doesn't know, but he does demonstrate both confidence in his crew and their capabilities, including capabilities they don't know they have yet. He asks for trust even in the face of uncertainty. It's the hallmark of a Starfleet officer that they maintain their crew even in the face of potentially dangerous situations.
I never expect lock step agreement.
I tend to agree on this: at this point Riker is not on board, Worf and LaForge are junior officers, Yar is herself on the first day on the job, the only remotely experienced officer we see that could feel qualified to question the new captain is Troi, but she probably senses that Picard feels he has good reasons to act this way and decides to go with it. The other experienced officer would be Data, but he tends to follow the chain of command and humans are still puzzling to him, especially in this timeframe.
