They didn't try but abandoned any efforts due to self interest of profits and economic extraction from a colony. The article put this in a better context, I just put excerpts from the link you shared:
Brits wanted to make sure they’d protected their economic interests before they departed, much the way they did in Singapore and Malaysia.
Another one:
In fact, in 1982, when negotiations began, the Hang Seng Index was already shaky due to fears that if China took over, the Communist Party would gut Hong Kong’s rule of law or nationalize wealth, causing the market to crash and capital to flee. The Brits needed to calm markets and ensure financial stability. That meant making sure the handover agreement protected British financial interests.
In the post-war decolonisation period GB had a policy of no independence before majority rule. They were putting in place democratic reforms elsewhere, and ensuring minority rule (ie South Africa) didn't continue after independence.
British corporations that existed in the HK market may have extracted revenue, as might any corporation, of any nationality with their overseas operations. The Hang Seng is a major stock market in its own right, so the majority of money was staying as HK money. The British government, on the other hand, was not receiving billions into the treasury as a consequence of holding Hong Kong.
Well they tried. Shortly after the Chinese revolution, HK was receiving an influx of refugees from China. Mostly well educated and skilled people. Britain was moving to bring in democratic reforms in the 1950s. China threatened to invade to "liberate" the territory if such reforms continued.
https://qz.com/279013/the-secret-history-of-hong-kongs-still...