How have coop board games prevented a player(s) from taking over decision making
Simultaneous choice is another method of forcing players to stumble over each other a bit. Space Hulk Death Angel uses this to great effect - players have to choose between their available actions, placing the card facedown, before all choices are revealed simultaneously and then executed in order. Robo Rally can be played in teams, and there you can really get in each other's way by accident.

"Active Player chooses" is another mechanism a lot of FFG coop games use to pass the decision making load around. Yes, everybody else has to keep their mouth shut while the player makes a choice, but if you aren't following the rules you're not really playing the game, are you? In a way I think this is a good way to allow table talk most of the time but give players short, important windows where they can keep from doing it.

Keeping everybody busy with their own problems seems a reasonable approach, and the LOTR LCG does this fairly well - enemies are dispensed from a central "staging area" to engage with a particular player, and in this way they fade from everybody else's view a little bit. I suppose a succinct way to phrase this approach would be "specialization".

Hidden information can be pushed farther than it is most of the time. Hanabi is an example of a cooperative game in which information sharing is really the central mechanic, and it's the first coop game I've played that really couldn't possibly be done as solitaire.

Narrative can also help remove the "single decision maker" problem by engrossing all the players in the events and giving them agency. I recently played a game of Mansions of Madness in which my daughter made some choices against my advice that cost us the game, but really they were in character for her (too much curiosity is what did it), and I was glad she felt confident enough to go ahead. We also talked afterward about lessons learned. :)

Lastly, regarding distrust, Shadows and Resistance each have a "bad" player from the start, but in some games (e.g. the Insanity mechanism in Mansions of Madness) a player can become bad, or have other weird behaviors emerge unbeknownst to the other players as a result of game events.

@matt points out in another answer that randomness (which is essentially information hidden from all the players) can help.