Hello Mongol_waaijer !
I was just reading your quote . YOu have pretty good lung capacity and without knowing your physical status . I am wondering ( since you were off the back quickly in cycling {with semi pro }, yet can run well ) ; could it be that your body is more suited to distance running than cycling ?
My second thought was , if you were racing in Holland , then it could be that the competition is just that much greater there than in most places at those levels since it is a national pastime / sport and mode to transportation .
My third thought was , how much did you train , I am assuming you were a cat. 1 or 2 , if semi pros were riding with you . If you were a true amateur and working for a living then training then racing against competitors that did a lot less working and a lot more training i suppose there is no harm done if you got dropped off the back . YOu did ok .
My last thought was , if you could run decent times as a marathon runner years later , could it be that you were not phsycologically suited for riding in the peloton .( running is quite a bit safer ) I have witness the last part for many years . Lots of people just cant ride in a peloton very well and end up going off the back , yet they are strong riders on their own .