The premise of the question is historically inaccurate.
Grand Duke Konstantin Nikolayevich (1827–1892), the Tsar's younger brother and head of the Naval Ministry, was a strong advocate for selling Alaska. He argued Russia could not defend it, it was unprofitable, and sale proceeds could modernize the fleet.
Emperor Alexander II ultimately approved the sale, but some in the Russian government (e.g., Foreign Minister Gorchakov, Finance Minister Reutern) debated terms. The Russian-American Company (which administered Alaska) resisted losing its monopoly.
Konstantin's support for the sale is sometimes misremembered as opposition because he later criticized the price as too low. But he never opposed the sale itself.