A sort of incomplete answer would be that the article is covering an important historical fact regarding the sixth-largest miltary in the world (by active personnel). 
Whereas the Zimmerman Telegram was a triumph for the intelligence community to catalyze US involvement in WW1 against Germany, Cable 1971 was prescient in that it foretold secession of East Pak from West Pak.
A Wikipedia article is all the more necessary since intelligence reports and commission findings are often ignored by world governments, which turn out to be inconveniently true retrospectively. Cable 1971 is just one of the many ignored reports.
Speaking of historical significance, since it’s a cable about conflict between two third-world countries at the time, it hasn’t garnered that much attention. But had it been related to some superpower, I am sure many leading newspapers around the world would had published countless articles on this cable.
Just my $0.02
Yes, there are thousands of them shared everyday but only a handful of them turn out to be as prophetic and foreknowing as Cable 1971. In the unlikely case should you have missed it, this cable was shared in December 1952, which warned that a nation found on hardcore religious principles might be divided into two, since minorities won’t feel safe.
As destiny would have it, that nation broke up in the year 1971. Co-incidentally the cable which augured this was also numbered 1971.
This stands out from the rest of the cables for its foresightedness of a nation breaking up and coincidence of conveying the year too.
PS - Fate, as it turns it, does have its own sense of irony
Really, though, it still seems weird to me. Would there still be an article about this if it wasn't numbered 1971? I assume that's just a sequential identifier, followed swiftly by Cable 1972, Cable 1973, etc. If the two correspondents were very significant figures in their respective branches, the article doesn't make that clear. It reads like just two mid-level officers in high command shooting the shit. And was the possible future breakup of this weird geographically-separated country really that unthinkable to all but a few visionaries back then? Of course it easy for me to say this now, but that seems like the obvious eventual outcome of such a bizarre setup. Surely people would talk about the possibility all the time.
Like imagine if next year the bottom falls out of the unicorn valuations completely and there's another dot-com crash. And then somebody discovers that Hacker News comment with id=2020, written all the way back in 2007, predicted that the tech bubble would burst sometime in the future. That's not really much of a coincidence because:
a) There had to be a comment number 2020, and
b) People on hn talk about tech bubbles popping all the time. If anything, the enormous time horizon between the prediction and the fulfillment would make it _less_ impressive.
If someone tried to pass that off as having some deeper significance, you'd think they were crazy.
To be clear, I'm not trying to assert that Cable 1971 is historically meaningless. Just that it comes off that way without a whole bunch of additional context that the Wikipedia summary does not provide in even a cursory way.
I too was curious of the significance of this article. This isn't really spelled out in your previous comment in such terms, you're assuming a lot of contextual understanding that I would hazard most people do not have of Pakistan.
(Spoiler: I just did)
Recommended read: https://en.wikipedia.org/wiki/1971_Bangladesh_genocide
Disclaimer: I am from Bangladesh (former east Pakistan)