It's not insane, it's rather on purpose. In the 1970s there was a huge concern that if proper infrastructure was built, it would cause foot and mouth disease to make its way from South to Central and North America, which stopped the USA's attempt to built a road across it. Within a decade, Panama turned much of the area into the Darien National Park and the UN classified it as a biosphere reserve & world heritage site because of a lot of the other concerns that came up during the attempt.
The epidemiological concerns haven't gone away and there isn't much interest in building across the gap.
> In the 1970s there was a huge concern that if proper infrastructure was built, it would cause foot and mouth disease to make its way from South to Central and North America
That's fascinating!
Wikipedia shows that the disease is nearly eradicated in South America:
The epidemiological concerns haven't gone away and there isn't much interest in building across the gap.