Maritime difficulties and the pirates along the coastlines of other countries.
Step-by-step explanation:
The trade route to India was one of the most prosperous in the ancient world due to India's cotton, spices, fruits and other great products that were exquisite.
It was also a little difficult to reach to India from many trade routers.
For Europeans, they had to circle whole of Africa and then go through Madagascar and its pirates to reach India in a long arduous journey.
There were many maritime diffuseness along the coast line with battling factions and Iran traders thus had to be careful too.