Unimaginative train operators

I was infuriated by the actions of the railway company SouthEastern and London Underground this morning, which added to the aggravation caused by the weather.

Due to an accident (I assume) Stafford Road between Wallington and the A23 was gridlocked, so my usual bus into Croydon was not likely to run any time soon.

I trudged through the snow to the nearest railway station and did manage to catch a train into London Bridge. It took nearly twice as long as normal, and when we arrived, London Bridge station was very congested. The Underground station entrance had been closed "due to overcrowding" (due to lack of trains I think). Everyone went to Platform 6 to try to get on a service to Charing Cross or Waterloo.

Several trains came and went, too full to take more than a few passengers. Then a half-empty one came in and stopped but the doors did not open. Eventually an announcement was made that this train was not due to stop at this station. But since it had stopped anyway at a red light, why didn't they open the doors and clear some of the backlog of frustrated passengers?