Lin Ruofu's tenure as prime minister for so many years is inseparable from his personal ability. He can counterattack a high-powered prime minister from a poor scholar with nothing, and he is resourceful and wise.
The Qing emperor was a king who was good at weighing. He has a way to balance Lin Ruofu's power and make Lin Ruofu use it for himself without threatening his imperial position. This is also one of the reasons why Lin Ruofu has been able to sit firmly on the throne of the Prime Minister for so many years. Later, when Fan was idle, the Qing emperor worried about how bad Lin Ruofu was and forced him to resign and return to China.
Lin Ruofu has been a prime minister for many years, and has accumulated many proteges and old collectors, with great power and wide connections. He is fully capable of influencing the political trend of the imperial court. He and princess royal have feelings for men and women, while princess royal holds the power in the library, and their combined political power is enormous.
As a prime minister, Lin Ruofu was also an important participant in the struggle for power. If the prince and the second prince can get Lin Refu's support, the success rate of succession is almost 100%. Lin Ruofu's son is a close friend of the prince and should support him. Only later, his son was killed by Wu Zhu because he obeyed princess royal's orders, so Lin Refu and princess royal made a clean break and decided to give all their political experience and capital to the future son-in-law Fan Xian, which directly affected the result of the competition for office.
To sum up, Lin Ruofu is in charge of the state power, and he has the strength and capital to influence the direction of the court, and even influence the result of the competition for office. He has great power.