[phil_folrida]

It is highly speculative to say Japan, even today we reference Native American as Indians.

He was thinking they reached India.

Same mistake today people do with Miles and Kilometer, when you are raised in one or another it is difficult to switch.

Erastothene was speaking in stadium, Columbus in Nautic miles.

The Spanish crown was motivated by greed.

[mannykannot]

At the time, the term "indies" was widely used for eastern Asia and eastern lands generally.

https://www.etymonline.com/word/Indies