Why do some people prefix people's names with "the"?

Lately I've been seeing a trend that I find disturbing for some reason, mostly in Indian publications but also in some American ones - prefixing people's names with "the". For example: The Mr. Gandhi said that taking the Narendra Modi's name was tantamount to committing a crime in the party.

Is this proper usage? It surely doesn't sound right.

It is not proper usage. As a commenter said, using the definite article with proper names is necessary and correct in some languages, and sometimes this gets carried over into English by non-native speakers (English language learners).

We do use the article with proper names in English in a very specific situation, not all that common, when you mean "people of a certain sort." Often when you do this, you make the proper name plural. For example,

The Mark Zuckerbergs of the world are changing the way we interact with one another.

You can find this with an indefinite article, too. For example,

She's quite a Beyoncé, breaking out of the group to have a successful solo career.

We also use the indefinite article with proper names in English when referring to someone we do not really know. Here's a typical example:

A Mr. Jones called to speak with you; he didn't say what it was about.

Hope that helps.

A name is sometimes prefixed with "the" to indicate a particularly eminent person, where there are other people of the same name who are less famous or not the person intended. For example, one might talk of the Michael Jackson, to distinguish him from this interloper.

While this would be fairly normal in conversation, it would be unusual in writing, because one can't put the emphasis on the the which is required.

I agree that the examples in the question are not correct or acceptable.  One exceptional and very idiomatic / idiosyncratic example in which this construct has become accepted simply through having been used (and because of the eminence of the subject) is “the Donald”, to refer to Donald Trump.  I can’t think of anybody else for whom this convention is used.

Related:

“You ARE Zaphod Beeblebrox?  ...  THE Zaphod Beeblebrox?”

“No, just A Zaphod Beeblebrox, didn’t you hear I come in six packs?”

:-)