I think most of your post was very sensible, but not the last point. MichaelAMW is right: there is a human element, and not everyone will sit meekly on the train while time goes by and various attempts to sort the problem fail to do it, especially if, as in this case, a station is very close.
If there are many factors that those dealing with the situation want to take into account, including the greater disruption to a larger number of passengers over a wider area if they detrain the people from the unit that's broken down, they will need to explain their thinking to those on board, and take action to alleviate the problems they may be experiencing - providing water, in this case. If they don't do those things they will give the impression that it's being handled in the interests of the railway, and some passengers will look for their own solution.
I already agreed that the needs of those onboard should be taken into account. There is no dispute over this.
Coming on to your point about explaining the decision-making process, it needs to be handled carefully as it may or may not have the desired effect. Commuters are a delicate bunch. Telling them that they are not going to be getting on their merry ways because it causes disruption to others is not necessarily going to go down well, and could make the whole situation worse. These things are better left to onboard staff to evaluate, and potentially better communicated to individual passengers should the issue be raised, if they see fit. Of course we have no way of knowing what was said onboard, and what went through the minds of those with decision-making responsibilities in this incident. There may be things that could have been done better, there may not. Until an investigation or review is completed and results published (which may or may not happen), none of us will really know.
Generally in my experience, most train crew are fairly good at explaining what the next step is planned to be, should they be aware of such information. It doesn't mean that was the case here, but again none of us knows.
The problem with perception is that people interpret things differently. I agree that being completely open about things is often better, but extreme care must be exercised in many cases as human psychology works in strange ways sometimes.
In my opinion it is very rich for someone to sit in front of the keyboard and just criticise, when it has already been explained by several people how things could pan out and may not have been what they appeared to be like, however I think I probably did overreact a little, so for that, I offer my apologies.
