when Vodafone came to India they bought an existing company called Hutch. They did not start from zero. So that's completely irrelevant.
And no they are not the leading telecom provider in India, most of the people I know have disconnected their Vodafone services in India and switched to Qtel. That's the general opinion over there.

I don't think Vodafone will completely trash Qtel.
Qtel has a lot of money (believe it or not probably comparable to how much Vodafone international has). If you can't believe that, they have very rich shareholders.
Unless Vodafone gives away free phones or something, or introduces rates which are half of Qtel's, they won't be too successful at first. And its unlikely Vodafone will do that, Vodafone is here for a return on investment, not to beat Qtel, snatch their customers even if they have to make a loss in Qatar.