"[wh-word] X [verb] Y?" in Indian English

In Indian English, you will often hear constructions like the following:

Why Lord Ayyappa isn't a avatar of Lord Mahavishnu?
Why each day of the week is dedicated to a particular god?
Why lord Shiva has a crescent moon on his head?

That is, rather than being of the form "Why [verb] X Y?", we have "Why X [verb] Y?". This occurs with all kinds of verbs (not just stative ones), e.g. "Why you went there?" for "Why did you go there?"; and also with other wh-words, e.g. "What you are doing?" for "What are you doing?".

I don't think I natively speak any variety of Indian English, but I've heard enough of it to know that the "[wh-word] X [verb] Y?" construction is considered perfectly grammatical (albeit I think it is proscribed in writing?). "[wh-word] [verb] X Y?" would probably be acceptable in Indian English, though I suspect it would mark you as a non-native speaker (of that dialect).

Now, as we know, this construction is ungrammatical in British English (and also American, for what it's worth). What I want to know is this: how did this construction come to be common and even grammatical in Indian English? Is this word order "calqued" (so to speak) from Hindi or something like that?

(If nothing else, I can say that the Dravidian languages probably have nothing to do with it - they're all SOV languages.)

For a general explanation, perhaps the fact that Indian-English is not a 'native' variant of English, in the same way that American and Australian variants of English are descended from British settlers centuries ago. In fact the majority of Indians who speak English consider it to be a second language, rather than a bilingual mother tongue. As such, many of the 'mistakes' by the original learners would have been gradually incorporated into the standard version of the language, and hence why your examples are grammatically acceptable in Indian English.

To offer a more specific (linguistical?) answer: as noted in this question and accepted answer over on Linguistics SE, English is quite rare in that it makes heavy use of Do-support. The verb do is frequently used as an auxiliary verb, especially in questions like the examples you provided. So:

Why did you go there?

Why does lord Shiva has->have a crescent moon on his head?

In Br/Am English

I am not familiar with the numerous languages spoken on the Indian subcontinent, but my guess is that not many of them have this feature of Do-support. Hence, it was trickier for the original learners to pick up on the Do-support, but they realised the need for a change in the verb conjugation.

(Much of this is speculative however, but hopefully it gives some idea of the possible reasons)