Just why is the District Line run so badly?

I rarely use it nowadays, thank God, but had the misfortune to use it
this morning (11th Janaury 2010), beginning my journey at Fulham
Broadway at 7.15a.m.

Firstly, the indicator boards at Fulham Broadway indicated that the
first train would be a "City" train, arriving in 2 minutes. Indeed,
the train did arrive in 2 minutes but it was an Edgware Road train.

This train then crawled along at barely more than walking pace all the
way to Earl's Court, and actually stopping for 2 minutes before
entering Platform 2.

There was then a 6 minute wait at Earl's Court - nobody could really
tell which platform the next City train would be on since the large
and historic indicator boards with the arrows are out of action.

Then a very full Upminster train arrived on Platform 2 from Fulham
Broadway, and about 1 minute later another emptyish one arrived on
Platform 1 from West Kensington. No announcements as to which would go
first but, obviously on the principle, "last in first out", the
emptier one on Platform 1 went first. On Platform 2 we were then left
standing for another 4 minutes, whilst we got fuller and fuller from
people arriving at the station.

Eventually we set off, again at little more than walking pace. At
several places we again came to a halt. There was a particularly long
stop just before the junction West of Gloucester Road, so I assume we
were either letting a "T Cup" train go ahead of us, or there was one
crossing our path going the other way.

We then started moving again, and mercifully my journey was only as
far as Victoria, but the train hardly went above 20 m.p.h. at any
stage of its long and tortuous journey, with several more stop-starts.

Just why is a District Line journey such a bloody slow and painful
experience?

Marc.