It wasn't so unexpected, was it? The forced exit of the former president of the People's Republic of China, Hu Jintao during the 20th Congress of the Communist Party sparked a wave of interpretations in the absence of a wider debate in China. First of all, it is the soft version. It was a health crisis. The former leader from Beijing would have felt sick during the meeting and have required help to be able to reach a safe place while waiting for a recovery. However, Hu Jintao is 79 and even if his hair turned grey, he is not known to be in a bad health condition, at least not one that might have determined his removal from the Congress. Moreover, the former president looked confused and amazed while being escorted out, an aspect that somewhat leaves room for the interpretation that it was not related to any of his health condition. There is also a middle version. Whispers would have reached the ears of the current president, Xi Jinping, regarding the possibility that his predecessor would vote unfavourably to Xi at the moment when unanimity gets in. Xi wanted to make sure that Hu had nothing to oppose to during the final outcome of the Congress. But there is also a hard truth. Hu Jintao would have been released from the Congress in a deliberate and forced way. His confusing stance while escorted might predict this. President Xi would have removed Hu to send a clear and general message to anyone who might violate his authority (either directly or behind the scenes), and particularly to his predecessor's predecessor, Jiang Zemin. Xi Jinping is a man of his times. Before becoming the party leader, Xi had a special appreciation for the party elders given that his father, Xi Zhongxun, himself, was a party elder before being politically purged by other party leaders. Turned president, Xi Jinping switched his tolerance for party leaders towards fearing that he could have the same fate as his father. Out of that fear, the Chinese president went on the attack. Hu Jintao might have been one of the party elders that Xi was afraid of, but the real threat to the current president is Jiang Zemin, the head of the Shanghai clique. By humiliating Hu, Xi wanted to show Jiang who really holds the power in Beijing. At the age of 96 and known to have various health problems, Jiang Zemin is far from any possible return to a position of power within the Communist Party, but he has sufficient political capital behind the scenes to influence a number of new party elders in the Shanghai clique. One of them might end up confronting Xi's monopoly of power. Moreover, Zhu Rongji, the 5th Premier of the People's Republic of China during Jiang Zemin's tenure, even at the age of 94, is expected by many to publicly speak over about Xi's economic policies, especially the 'Zero-Covid' agenda. Hu Jintao, unlike Jiang Zemin, remained in the shadow since 2012 when he stepped down to the detriment of Xi Jinping. He is not expected to possess the similar level of political capital of his predecessor. Moreover, Hu is a member of the Communist Youth League, clique that almost disappeared under Xi. Not the same can be said about the one from Shanghai. It is true that the draconian quarantine imposed on Shanghai would have had the purpose of creating popular agitation against the local leaders and thus the political weakening of the Shanghai clique. It is also true that in the absence of a cult of Xi's personality unseen since the death of Mao Zedong in 1976, the next leader of China would most likely have been from the Shanghai clique. Xi Jinping might not have respected then disliked the party elders if it wasn't for his father, but there is also another lesson that Xi might have also known from the past. When the politics get messy in China, the party elders come back to the fore, challenging the new party order by either changing or repositioning the chess pieces. During the 1989 Tiananmen Square protests, known in Chinese as the June Fourth Incident, because of student demonstrations and party fragmentation, then paramount leader Deng Xiaoping recalled seven party leaders in order to calm the agitated crowd and unite the party around a common cause. The Eight Immortals, as they would be known after the originals from Taoist folklore during the Tang and Song dynasties, reclaimed political authority, led a forceful intervention to end the protests, and purged then Secretary General Zhao Ziyang, on the paper the most powerful figure of the party, but de facto in Deng's shadow. Xi Jinping could now be in Deng Xiaoping's position trying to ensure that no future Zhao Ziyang would accumulate enough power to become the party's paramount leader. Or Xi might be afraid not to end up in the mortal position of Zhao Ziyang and get banished by the next generation of Eight Immortals.
President Xi Jinping wanted to draw a clear line: in the absence of people, the tea gets cold and party elders must change their mentality and accept their new position within the party. Would they not do that, they must bear the consequences.

Bibliography:

Andrew J. Nathan, The Alternate History of China (Review Essay), Foreign Affairs Magazine, September/October 2022, Book Review: "Never Turn Back" by Julian Gewirtz | Foreign Affairs

James Palmer, What the Hell Just Happened to Hu Jintao?, Foreign Policy Magazine, October 22nd, 2022, Did Xi Jinping Just Purge Hu Jintao at China's Party Congress? (foreignpolicy.com)

Julian Gewirtz, China's Road Not Taken, Foreign Affairs Magazine, September 29th, 2022, China’s Road Not Taken: How the Chinese Communist Party Rewrites History (foreignaffairs.com)

Melinda Liu, The Party Elders Who May Challenge Xi, Foreign Policy Magazine, October 13th, 2022, CCP Congress: Party Elders May Challenge Xi Jinping (foreignpolicy.com)