A large portion of South Wales is small towns and villages built on hills and mountains, so it's difficult to cycle from place to place for most people. Mid Wales tends to be very spread out and hilly, so again, difficult to cycle around unless it's for pleasure. If you cycled to work, you'd probably be very sweaty by the time you got there.

E-bikes have been invented for a while now

Have a look at Google Street View to see how steep some of our hills are. They're great for a challenge, but you definitely wouldn't want to tackle them on a cold, wet, Welsh morning on the way to work.'

This is just bog standard "It wouldn't work here" stuff. It gets cold and wet elsewhere and it doesn't stop people from cycling

Even the main road going north to south through the country is a single lane in each direction for the majority of it.

That's a policy choice not an inherent condition of geography. Switzerlands full of mountains and they have good trains.