Stalin didn't exactly trust Mao as Mao rose to power by and large independently from him unlike most of the other communist heads (excluding Tito).
Actually, Stalin and the Comintern were crucial to Mao's rise:
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"Nor was Mao demoted by the Comintern and the "returned students" for his failure to follow Moscow's strategy. The opposite is true: Mao was Moscow's chosen man. The story started on 21 July 1932, when the Shanghai Center criticized the Central Bureau in Jiangxi headed by Zhou Enlai of not being aggressive enough in military operations. Zhou thus left the rear base to join Mao, Zhu De, and Wang Jiaxiang at the front. In September, the four men at the front disagreed with the other members of the Central Bureau who remained in the rear. The former wanted to give the troops a seven-day respite since they had fought three successive battles in the past month, while the latter wanted them to fight a battle in Yongfeng where enemy troops had gathered. The difference between the two sides was purely technical, if not trivial; there was no "two-line struggle" whatsoever. The four men at the front proposed on 25 September that a meeting of all members of the Central Bureau be held. When all the members met in Ningdu in the first week of October, Mao's argument apparently became unpopular, and he was criticized for being "rightist." Some proposed that Mao leave the military command, and Zhou, who was presiding over the meeting, suggested two alternatives: either Mao be the commander while Zhou served as overseer; or Zhou take command, with Mao acting as assistant. Mao rejected the first alternative. The meeting accepted the second one, but Mao asked for a "sick leave" to stay at the rear, and the meeting granted his request. The Shanghai Center endorsed the meeting on 6 October,
"This was how Mao left his military command. His egotistic personality led him to clash with his colleagues, and the Maoist story of Mao's demotion due to his opposition to Moscow's policy line is a Iie. The truth is that when Mao was in difficulty with his colleagues at home. Moscow came to his aid. In the Fifth Plenum in January 1934, which was regarded as the peak of the Wang Ming line by Maoist historians, Mao's position in the Party was upgraded from an alternate to a full member of the politburo, This was largely due to the Comintern's intervention on Mao's behalf. In March 1933, the ECCI telegraphed the CCP Center and stated that the way in which Mao was treated "must be gentle and comradely, and Mao should be allowed to undertake a leading position." The Center subsequently relayed this directive to the rank and file, Throughout 1934-35, Mao's name frequently appeared in the Comintern's publication and the reports of the CCP's delegation in Moscow headed by Wang Ming. In these documents, Mao was praised as “the leader of the Chinese soviet movement," and the "preeminent young politician and military strategist of the Chinese Soviet Republic, Moscow even published a volume of his selected works, probably the first of its kind. In October 1934, Mao's work on guerrilla warfare was printed by the CCP's Central Military Committee as its instruction to the rank and file. At the Seventh Congress of the Comintern in 1935, Mao was praised as an "outstanding and valiant standard-bearer" of the communist movement, the same praise as Dimitrov received. In Moscow's exhibition hall of CCP history, the only personal portrayals of CCP leaders were Mao and Zhu De. In
Pravda of 13 December 1935, and the
Communist International, nos. 33-34, 1935, Mao was praised highly as the "legendary leader of the Chinese people" and the "first one who recognized and openly exposed the Chen Duxiu capitulationism." It was this kind of unprecedented support and endorsement from Moscow that paved the way for Mao's rise to power at Zunyi.
"Mao's victory at Zunyi was also attributable to the support of the key members of the "returned students" who understood that the Comintern favored Mao. In November 1934, the CCP delegation in Moscow headed by Wang
Ming informed the Party Center that the Comintern considered Mao an experienced leader. It was not a coincidence that shortly after the Moscow message, two key members of the "returned students," namely, Zhang Wentian and Wang Jiaxiang, became closer to Mao and more receptive to his opinion. It was after Zhang and Wang had leaned toward Mao that Zhou Enlai came to Mao's side, followed by Zhu De. Thus, Mao gained the support of the majority in the Politburo, and he became increasingly vocal in criticizing the military conduct of Qing [Bangxian] and [Otto] Braun. On 12 December 1934, an emergency meeting, presided over by Zhou Enlai, was convened to discuss military strategy. Qing and Braun insisted on following the previous decision to head toward the central Hunan area. Mao contended that the new base area should be on the border of Hunan and Guizhou. Zhang and Wang voted for Mao first, and then Zhou swung to Mao's side. Thus, for the first time, Mao overrode the Qing-Braun decision. A week later, a Politburo meeting further confirmed Mao's strategy. It became clear that Mao had gained the upper hand in the Politburo with the support of the "returned students." This was not due to his "correct" strategy because Mao's idea to head toward Guizhou was soon proven "wrong" and abandoned.
"Suffice it to say that before the Zunyi conference, Mao was not in conflict with Moscow and he had no reason to stage an anti-Moscow "coup" at Zunyi. In fact, Mao was supported by the Comintern and the key members of the so-called "returned students," and his loyalty to the Moscow-led world revolution remained intact. This becomes more evident when a fact, which has long been kept secret, comes to light: Mao was responsible for the restoration of radio communication between the CCP and Moscow...." Michael M. Sheng,
Battling Western Imperialism: Mao, Stalin, and the United States, pp. 19-21.