To restate RO's question: Considering the pilot's experience, he should have known that the safest option was to land straight ahead. However, he chose a course of action that was less safe, so the question is what may have motivated him?

The convenience factor is the most obvious one, but there may have been one or more other factors at play, such as:

The copycat factor, which makes you inclined to copy something that you saw someone else do in a similar situation, without thinking things through. In this case the Discus pilot successfully completed an abbreviated circuit a short time before the accident. This factor was mentioned in the AAIB report.

The vanity factor, in the context of which landing straight ahead could have meant an implicit admission that the Discus pilot was more skilful.

The improvisation factor 1, whereby prior to taking off the pilot didn't consider all the relevant circumstances (including turbulence, wind shear, etc.) and didn't come up with a definite and well thought-out plan on how to handle different emergency situations, should one arise during the take-off..

The improvisation factor 2, whereby prior to taking off the pilot did consider all the relevant circumstances and did come up with a definite and well thought-out plan on how to handle different emergency situations, should one arise during the take-off, however, upon encountering the emergency situation decided to change his plan.

Branko
XYU