Instead of a troika coming to power after Lenin’s death in 1924, what happened?

Stalin took the whole control in the country.

Explanation:

After Lenin's death in 21.1. 1924 Stalin, Kamenev and Zinoviev jointly took over the management of the party, ideologically positioning themselves between Trotsky (representative of the left wing of the party) and Bukharin (on the right wing of the party). During this period, Stalin renounced the traditional Bolshevik doctrine of implementing the International Revolution in favor of a policy of building socialism in one country, which was in direct contradiction to the theory of the Permanent Revolution, which was created by Trotsky. Stalin will soon change sides and cling to Bukharin. Together they opposed the opposition made up of Trotsky, Kamenev and Zinoviev. Until 1928 (the first year of the five-year plan) Stalin became the supreme leader, and Trotsky was exiled the following year. Having succeeded in defrauding Bukharin's right wing of the party, Stalin advocated collectivization and industrialization, and can be said to have fully taken control of the party and the state.

Very useful. it is to learn because history repeats itself so learning about it those mistakes not happen again.