An easier way to prevent Lenin's arrival into Petrograd is to have the Germans refuse to send him there on a sealed train.
He doesn't have to die for there to be no Russian revolution.
IMHO I don't believe that it was a coup. The October Revolution was a process lasting several days, beginning with the Provisional Government seizing the Bolshevik press.
The Military Revolutionary Committee (or MRC) was predominately Bolshevik but was primarily an organization under the direction of the Petrograd Soviet.
Furthermore, the Provisional Government by October 1917 was bankrupt, with Lenin urging his party away from supporting the Provisional Government.
After all, this was a government which launched a massive offensive along the Eastern Front even after it said it would only be fighting a defensive war.
It failed to carry out land reform. Fuel shortages were still prevalent in Petrograd. The war hadn't ended yet (and in fact had intensified), etc.
The October Revolution was the result of these many factors.
the soviets had been effectively operating alongside the Provisional Government in a phenomenon known as dual power.
Sooner or later the Provisional Government would either have to make a move against the soviets, or the soviets would have to make a move against the Provisional Government.
In the election that did happen (after the Bolshevik national seizure of power) Social Revolutionaries, as I understand it a peasant party easily won.
The Right SR Party had split in 1917 into a Left SR Party, which joined the Bolsheviks in a coalition government after the Second All-Russian Congress of Soviets.
The thing about the Constituent Assembly was that it did not differentiate between Right and Left SR; only the Right SR party was represented, even though the Left SR party had gained a significant following in the countryside over that of the Right SR party.
The Bolsheviks, if the Left Party had been represented inside the Constituent Assembly, very well could've have won a majority with their partner the Left SR party.
The Constituent Assembly was shut down because the Bolshevik-Left SR parties saw it as a threat to soviet power.