In 1973 they replaced the canal with a road, since… cars go vroom vroom and need space, but this was reverted between 2010-2020.

no, they built a canal later

Pretty much, yes - the Stadsbuitengracht was a defensive moat originally, then they converted part of it into a motorway in the 70s.

Not uncommon. Cities grew and the aqueducts just went director to their river, si they suck and paving them was a good excuse to get rid of the sanitation problems they had while expanding car infrastructure. Cities today know better and built aqueducts that didn’t dump everything to the river.