Why build the Corinth Canal?

Why build the Corinth Canal when ships could sail around the Peloponnese?

A shorter canal passage promised to make the voyage quicker and cheaper, with earlier work on the route providing another reason to proceed.

Sailing around the Peloponnese remained possible, but a canal promised a shorter and cheaper passage. That saving in time and distance explains why completing the route appeared attractive. Earlier work on the route is also offered as a reason to proceed.