Stalin was a Marxist revolutionary from a very early age, and I don't know of any reason to believe that he wasn't truly committed to communism. It's true, though, that collectivization helped him further his political goals, but in a rather different way than your question seems to suggest.

As I'm sure you know, the peasantry made up a huge portion of the Soviet population, and this posed both an ideological and a practical problem for the Bolsheviks. As Marxists, they held that the material conditions of the proletariat inclined it to socialism, while the peasants' material conditions inclined them to capitalism -- after all, farmers working their own land retained control of the means of production. This is why Marx famously said that the socialist revolution would come first to Western European countries, whose growing industrial economies were depleting the peasantry and strengthening the working class. Lenin provided some theoretical solutions to the ideological problem, but the practical problem was much trickier: how do you build socialism in the countryside while still producing enough food to supply the working class, and anyway, what does socialist agriculture even look like?

Under the system of "war communism," the Bolsheviks instituted quite draconian policies intended primarily to get control of the resources necessary to beat their rivals in the Russian Civil War. One of the most important elements of war communism was grain requisitioning, which helped keep the Red Army more or less fed but provoked serious unrest among the rural population. After the Bolshevik victory, the most important issue now was rebuilding the shattered economy and establishing some sense of social order, both goals for which the policies of war communism would have been completely counterproductive. The result was the New Economic Policy, or NEP, which brought an end to grain requisitioning, and allowed farmers to sell some of their produce. On the one hand, the NEP was great for the regime, because it both reconciled the peasantry to Soviet power and increased agricultural production. On the other hand, though, it represented its failure to bring socialism to the countryside, or even to encourage more modern farming methods and technologies. Even more dangerously, as the Bolsheviks saw it, the NEP enabled entrepreneurial or well-positioned farmers to accumulate wealth and exploit their neighbors -- that is to say, to become capitalists. Furthermore, grain prices were increasingly falling while prices for industrial goods were rising (the famous "scissors"), leading Soviet farmers to produce less grain for the market. Bolshevik leaders agreed that policies had to change, but were divided as to how, and Stalin skillfully used these divisions to maneuver his way into power. He initially sided with Bukharin, who supported the gradual expansion of collective farms on a voluntary basis, believing that this would convince farmers of the superiority of socialist agriculture, against Trotsky, who favored rapid industrialization to drive down the price of manufactured goods.

In 1928, the unfortunate economic trends of the previous years came to a head, and the state was not able to buy the amount of grain that planners reasoned it needed to feed the population. Stalin blamed this grain procurement crisis on a "strike of the kulaks" -- those same wealthy peasants who took the opportunity provided by the NEP to become capitalists -- and implemented emergency measures to seize grain from wealthy farmers. This atmosphere of crisis served his political purposes well, inasmuch as it allowed him to throw Bukharin straight under the bus and eliminate a possible internal threat to his power (Trotsky had already been marginalized and would leave the USSR the following year). What it absolutely did not do is make the peasants rebel less. The NEP allowed the Soviet peasantry to live with the regime, but Stalin's revival of the practices and ethos of war communism alienated them from it completely. Forced collectivization sparked rebellion and resistance throughout the Soviet countryside.

Overall I think u/nelliemcnervous has a great answer.

What I would want to additionally highlight is that there was very little overall debate on the necessity of destroying private control of farms. The larger argument was not really 'should we do it' but rather 'when should we do it'. This is clearly not some scheme Stalin cooked up to to gain control, but rather had been central to communist vision since the beginning.

Also, I would argue the peasants were not actually all that rebellious in any direct sense. It was more that they simple didn't sell their grain for the prices the Communists wanted. You can call that a 'passive rebellion' or you can simply call it buissness. There was certainty no political anti-communist revolution in the country side in 1928.

Alexei Rykov the second most powerful person behind Stalin (unfortunately often ignored today) in the late 20s absolutely agree capitalism in the country side could not stand. His principle opposition was not ideological, but practical. He believed that the state hardy had the capacity to do this effectively and it would result in a gigantic catastrophe. It would great a huge amount of instability both political and economic, it would lead to peasant fighting the regime and there would likely be food shortages.

We have to understand how little influence the party had outside of the city. All the banners you see in propaganda quickly ended when you left urban environments. The party bureaucrats that did exist in the provinces was marrying their daughter to the "kulaks". They did not really want this collectivization either.

In effect, Stalin took a huge personal risk by going into this effort, and it was a huge risk for the regime as a whole. He quite literally had to create the tools and institutions to do it on the fly (armies of factory works as shock troupes and so on). The results of this collectivization drive was far worse then people like Rykov had assumed. Stalin faced extreme internal pressure to stop these polices, and in fact he multiple times retreated on this issues, but after a while ramped them back up.

While once it was all over, Stalin certainty was more powerful and dominate to get there he had risked everything. Facing opposition inside the party, from the peasant population as whole and he at that point was incredibly weak to foreign attack.