650B Elephant National Forest Explorer

Ed will be here shortly to elaborate, but the bike is designed to handle better with the front load. long rake/short trail geometry.
It's an old french thing, now adopted by some of the American rando nerds too.

Very much this.

Trail = distance between axle and headtube;

Track bike typically have 65mm trail, quite a high trail for high speed stability but feel crap at low speed (ever wonder why people like putting higher pressure tyres on their track bike on the road? now you know).

Road bike typically have 57mm trail, not as high as a track, but still give you a nimble ride with a bit of stability, this is the de facto choice of trail.

Rando bike have a much lower trail, around 35mm, they're much quicker than road bike and can feel extremely nimble at high speed without a front load.

Add a front load, it slower the steering, but enough to make it more like a road bike but with the additional benefit of being able to micro-correct your steering more while cornering (hence handle better).

Jan Heine wrote it well in his blog about the discovery of the front-end geometries;

Then I started riding an old Alex Singer randonneur bike (see above) once in a while. The Singer surprised me: “Tricky” corners suddenly were less difficult. When I noticed a pothole too late, and thought that I would not be able to steer around it, I braced myself for the impact. To my surprise, the bike responded quickly enough to avoid the pothole. When I got tired, the Singer was easier to keep on a straight line – in fact, I could ride on the white painted “fog line” for miles with little concentration (see photo at the top of the post). Riding no-hands at moderate speeds was easier, too. This confused me: The Singer had “quicker,” more precise steering, yet it was more stable.

When I switched back to my normal bike after a single ride on the Singer, I found myself running wide in corners. I hit potholes that I thought I would miss. And the bike sometimes weaved unexpectedly when I was getting tired. Both bikes had a similar positions, both had handlebar bags, but something was different. To my surprise, the bike I rode all the time felt less intuitive than the new-to-me Singer.

That is when we started measuring geometries. We realized that the Singer’s geometry was anything but the “relaxed” geometry we had expected. The bike had a steep head angle and less trail than was common at the time.

Still doesn't explain why you put the weight so high up when you could have a low-rider front rack.

Because it make little difference, otherwise courier with big fuck-off Grobag would be falling arse over pierced tits all over London.

Can someone explain to me in simple terms why this bike has so much weight attached to the steering end and nothing at all over the back?

miro answer your question, because the weight distribution is much more even with a front load, than a rear load when a rider sit on it, climbing became easier because of the additional weight on the front, descending also easier due to having more weight on the front, especially with a low trail geometry making it easier to turn tighter letting the front weight "flop" the wheel.