It was built in 1887 so it's just people of that time trying to reference older architecture. But they also had to mash it up with all that steel work. The entrance looks pre-industrial but it's mashed with post-industrial engineering. In fact, that's why they kept the curves in the remodel. They're structural but they're also modernist in style which is why it works with the modernist design.

Plus this period was Imperial Germany. So it makes since why the entrance looks all castle-y. You can draw both the industrial, modernist aesthetic coming into being and the old traditional style remaining from that.

Obviously 1959 Germany was a totally different environment given what happened. So that expresses itself too. Which includes carbrain. Although the original bridge was built for cars as well. So it's not like they ruined a pedestrian bridge in favor of cars. The whole point was cars to begin with. And other bridges were to facilitate trains.