Following the link in the second paragraph of the article, "new Belt and Road action plan," leads to a question-and-answer type article. The answer to the second question of CSIS's article, says (last sentence of second paragraph):
At a time when many large state-owned enterprises are struggling to stay afloat and banks are stuck in a cycle of rolling over ever-growing and progressively less viable loan portfolios, the projects that make up the Belt and Road could provide vital life support and serve as a useful patronage tool for compensating vested interests threatened by efforts to implement market-oriented reforms.
From that, I understand the vested interests as being the state-owned enterprises and banks. So, the definition of patronage (from M-W's Learner's Dictionary) most applicable in that context would be:
1: money and support that is given to an artist, organization, etc.
The New York Times has an article from 2010 that gives some insight into how China Fortifies State Businesses to Fuel Growth. The part of the article concerning how governmental patronage works is towards the end:
Some analysts argue that the state-owned conglomerates, built with state money and favors into global competitors, have now become political power centers in their own right, able to fend off even Beijing’s efforts to rein them in.
Of the 129 major state enterprises, more than half the chairmen and chairwomen and more than one-third of the chief executive officers were appointed by the central organization department of the Communist Party. A score or more serve on the party’s Central Committee, which elects the ruling Politburo. They control not just the lifeblood of China’s economy, but a corporate patronage system that dispenses top-paying executive jobs to relatives of the party’s leading lights.
China’s leaders have sought occasionally in the past year to curb speculative excesses by state-controlled businesses in real estate, lending and other areas. In May the State Council, a top-level policy body sometimes likened to the cabinet in the United States, issued orders to give private companies a better shot at government contracts — for roads and bridges, finance and even military work — that now go almost exclusively to state-owned companies.