I'm not sure Riker is that influential in the episode. First Troi warns Jellico about the crew being unsure of him. Then Geordi himself complains to Riker first about the orders and lack of time to complete them. Presumably the crew are complaining all over the place and Riker's had to hear it since the shift rotations. And he's stuck between them and a captain who does not listen to him. So in addition to losing Picard he's also going to lose all respect of his crewmembers by becoming a Jellico style first officer and enforcing his changes
It's his job to enforce changes. How he goes about doing that will determine how every other officer under him might behave in response. If Riker is a dissident, then it sets the precedent that it's acceptable for the rest of the crew to be so. If he stands there & tells Geordi that the captain is not going to listen to him, without knowing why the captain isn't taking any of his suggestions, it undermines the captain's authority, suggesting that he is a tyrant, when no one, Riker included, knows that to be factually accurate. There are other possibilities, which Jellico hasn't explained, & being that he's the captain, responsible for the oversight of the mission he's been better briefed on than any of them, he needn't have to
My point was that once Riker is gone, there are no more dissidents. You don't hear the new 1st officer telling Jellico about any crew issues. That supports the notion that they weren't as big a hardship or bad judgement call as Riker painted them, which tends to suggest that his own attitudes might've shaped the crew's morale just about it just as much as any hardship Jellico laid on them
No, he had a problem with alienating his essential staff and causing undue disruption in the run-up to combat. Rookie mistake, but a potentially fatal one.
Who's to say it's undue? Do we normally see a captain ripped from his command & some other one spontaneously dropped in there, on the brink of a military conflict? It's just as likely that the "disruption" was ultimately unavoidable given the circumstance.
If there's a failure in why this changeover doesn't go swimmingly for the people it effects, it is far more likely to be a symptom of the actions of high command, making the call to do this in the first place, & Jellico is just as much a victim trying to make due with what he's been dealt, in order to achieve what he's been tasked with, as any of his subordinates.
That Jellico doesn't engage in dialog about what his reasons are, for his orders, doesn't make them deliberately alienating or unduly disruptive in themselves, if he is in some way justified, beyond their capacity to know it, & the privilege of rank is that he doesn't need to justify them.
Rank is maybe the only thing he's got going for him in this entire ordeal, as a way to get the job done. No one wanted Picard to be reassigned. So Jellico's default state is "The guy no one wants". If the mission is critical & time sensitive, that puts him in the hole from the get go, & rank is all he has at his disposal to give him an advantage for mission success with a bunch of reluctant strangers
The man is clearly not a rookie. He's probably a Cardassian War veteran commander, to know so much about how to deal with them. You don't learn how to deal with an ex-enemy as well as he does without being out there doing exactly that in many encounters