Well, part of the reason that so many native Russian and Ukrainian anarchists were excited about the October Revolution is that they had participated in making it, and figured that the Revolution was a big step towards the realization of power in their lifetimes. In 1917, the issue was not so much that they trusted or were excited about the Bolsheviks or Party communism, but rather because the Bolsheviks were only one of many different factions involved in the October Revolution, and often not the most important. Their enthusiasm about the whole project started dropping off in mid-1918-1921, as the state socialists started seriously putting together their workers’ state, the Bolsheviks started moving to consolidate power within it (with the Civil War serving as the health of their state), and the Bolsheviks formed up the Cheka and the Red Army and put them to work imprisoning and shooting anarchists. Most of the exiles from out of the country started arriving toward the end of that period (e.g. Goldman, Berkman, and most of the other exiles from the Palmer raids arrived in January 1920).