400 YEAR OLD MAPS DEPICTED CALIFORNIA AS A ISLAND

There's a piece of California history where it was once mapped as an island.

Now according to mainstream history when Spanish explorers first arrived in California, they seemed to have mistaken it for an island.

Apparently the island of California stretched nearly the entire North American Pacific coast and was thought of as an island paradise. They say that it was one of the biggest mapping errors in human history.

But how does a mistake like this even happen? AND why did California Island still appear on maps for centuries after it's initial discovery, and what caused k cartographers to be so split on the issue?