Assume your AccountUser class has the schema equal to the object you push() in your javascript.

As @dbc mentioned in comment, either change your JSON.stringify() code like:

var jsonData = JSON.stringify(users);

Or change your backend C# code into:

class UserList 
{
    List<AccountUser> Users {get; set;}
}
[HttpPost]
public bool GeneratePassword([FromBody] UserList users)
...