Clearly the principal reason why EDI and BFS have failed is owing to a lack of early morning / late night rail services rather than insufficient demand.
Naturally the holiday routes are less dependent on rail connectivity, hence why early morning departure / late night arrival times have not precluded their success.
I see your point but the lack of rail services at these times ultimately results in insufficient demand. The fact rail services to London take longer than from other airports, even if only by 10 minutes and are on a general commuter service rather than an airport service like the Gatwick or Stansted Express is also likely to effect appeal to business passengers.
Also as I mentioned the more limited options in terms of hotels, car parking, transportation, shopping or business lounge services also is likely to impact.
You are definitely right in saying holiday routes are less dependant on rail services, not to mention all those other facilities so they of course as it would seem perform much better.
If the profile of routes matches this, why is this necessarily a problem?
Because EasyJet have clearly come in with an intention to serve both domestic and business travel alongside leisure passengers and have been unsuccessful to a degree. They are now more limited to focusing on leisure based destinations which limits and reduces growth opportunities for the future.
Whilst this is much less of a consideration, it means some aircraft may have to operate quite inefficient schedules whereby the last flight may arrive at only 8 or 9pm or the first doesn't leave until 9 or 10am as there are very few short sector flights remaining. This can result into what is known as "slot sitting" where often shorter flights are scheduled simply as it is more profitable to fly something rather than nothing at all, not necessarily because the level of demand requires it. This maybe what is happening to the Amsterdam route when it goes to 3x daily in the spring.
Surely the initial success of these routes was a pre-requisite for the complete transfer of these routes?
The reality is there is one of two reasons to explain this:
1. There is not sufficient demand to support the viability of services on these routes from both airports
2. EasyJet is squeezing naturally healthier yields out of Southend by forcing this area of the market (predominantly Essex) to use Southend by closing duplicate routes at Stansted (in other words, people who would have chosen Stansted for these routes now have to go to Southend since they no longer have the choice to use Stansted if they continue to use EasyJet).
Take your pick, but my vote goes to the 2nd one. EasyJet used to fly easily up to 3x daily on Alicante, Faro etc. from Stansted alone only 2/3 years ago and now only once or twice daily from Southend. There is certainly enough demand to support the viability of these routes at both airports. Instead EasyJet clearly just chooses not to for strategic reasons.