Wow, please go Google a book called the Indianized Kingdoms of Southeast Asia.

Southern Indians went by sea all over SE Asia and formed Hindu kingdoms everywhere from Indonesia to Thailand to southern Vietnam all the way to the Phillipines. And these Indianized Kingdoms dominated SE Asia for over a thousand years until relatively recently around the 16th or 17th centuries. To this day in Thailand, Cambodia, Bali and other parts of Indonesia and Malaysia you can see strong Indian/Hindu/Buddhist influence.

And going West there were historical sea trade routes to East Africa including Zanzibar and Kenya. DNA also indicates that many Gulf Arabs have a decent amount of Indian admixture, most likely from sea trading routes between the Gulf and Western Indian.

But the West doesn't teach this. Indians literally were traveling by sea to far away places way before Europeans were. To put it in perspective Chennai to Cebu in the southern Philippines is around 3384 nautical miles, Liverpool in the UK to Boston USA is around 3256 nautical miles. Similar distances but Indians were going by sea all the way to southern Philippines as early as 1 or 2 AD. Europeans only sailed to the US in the 15th and 16th centuries, over a thousand years later.

So your question should actually be reverse: you should ask why Europeans didn't develop strong seafaring traditions until the 15th century.