The view with most traction now is that it was a much more self serving move for Russia. During an increased period of tension with Europe over their treatment of the Poles, Russia wanted to make sure in case of war their fleets would not be stuck in port. By being across the Atlantic they could freely begin a Guerre de Course war on British commerce if need be. Whereas during the Crimean war their fleets had been bottle necked in the Baltic and Black sea and unable to reach the vulnerable trade routes and were less valuable for it.

This fine JSTOR article from 1915 actually holds up quite well and lays out the general situation and the specifics of the Russian Navy at the time: http://www.jstor.org/stable/1835544?seq=2#page_scan_tab_contents