Mainstream media reports suggest the fandom is genuine.
So, like, likable: Tony Abbott's Facebook popularity soars thanks to Narendra Modi indicates that Indian PM Narendra Modi has a lot of facebook fans, and getting mentioned by him may have slashdotted Abbott:
But a spokeswoman for Mr Abbott said the increased traffic was genuine
and that no "likes" or advertising had been purchased for the Facebook
page.
"It is no secret that the Prime Minister hosted a number of world
leaders in recent times, including Indian Prime Minister Narendra
Modi," she said.
"These visits attracted large international audiences to the Prime
Minister's social media channels, thus generating a spike in organic
engagement with the page."
Earlier this month Mr Modi posted photos with Mr Abbott during his
visit to Australia for the G20 summit.
Mr Modi has more than 25 million Facebook likes and 8.17 million
Twitter followers. A selfie with Mr Abbott posted to his Facebook
account with the a caption that read "With my friend Tony Abbott at
the MCG" received more than 710,000 likes and was shared more than
11,600 times.
Other photos of the two leaders also received hundreds of thousands of
likes.
Mr Modi is particularly popular with young Indians and has been dubbed
the "rock star Prime Minister".
Tony Abbott’s Facebook popularity skyrockets all thanks to one selfie argues that Abbott's spike in popularity coincided with a November 18 selfie with Modhi (note: false bottom graph)
(Note: graph is from Tony Abbott is Mystifyingly Popular in New Delhi's Facebook Community)

Tony Abbott is Mystifyingly Popular in New Delhi's Facebook Community (by Pedestrian.tv) notes that his Indian likes are still in the minority:
Statistics gleaned from social media analysis site Social Bakers
indicate that somehow, even if the popular majority of Prime Minister
Abbott's fans are 18-34 year old New Delhi residents, his newfound New
Delhi fan base only accounts for 15.5% of his total audience.
Socialbakers has looked at Tony Abbott's popularity by country:
Australia 287 887 fans, 72.8%
India 61 287 fans, 15.5%
United States 5 005 fans, 1.3%
No other country had more than 1% of his fan base.