हम उस देश के वासी हैं, जिस देश में Shiv Ganga दौड़ती है

Yes, popular demand.

There were no trains to Delhi on the Wadi-Daund in the 80s, and connectivity between Bangalore and North Karnataka was also not sufficient.

When KK was diverted via VKB,SC,...
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the people and politicians from North Karnataka demanded that it be regularized via Gulbarga so that the train serves the state better (otherwise, only SBC and RC were the only major places served by the train).

Also, places like Bijapur were on the MG back then. Passengers from that area would travel to SUR by MG and switch to KK there for going to Bangalore or to the North. So, there was a lot of demand to run KK regularly via Gulbarga.