The Russian Civil War is a historical event that fascinates me, but one that I never did learn very much about in my history classes. From my admittedly rather simplified understanding, the main reasons why the White Russians lost were as follows:
The first two points were explained rather well in previous r/askhistorians threads, but the last one continues to baffle me. I know that the White Russians were not a unified force: it's a blanket term referring to many separate, smaller forces that were led by former Tsarist officers. But why were these various factions unable or unwilling to work together? Did they have radically differing superobjectives beyond defeating the Communists? Was it a matter poor communication that prevented them from coordinating their forces? Or are there other factors I've missed entirely?
There were a few different reasons as to why they never linked up. Distance was a big factor. The Allies sent in forces to help fight the Reds, but they landed at Arkhangelsk and Vladivostok. Complete opposite sides of the country. Many whites didn't fight once the Allies showed up, expecting the Europeans and Americans to do the fighting for them. The Reds were in power in the cities, where it was easier to concetrate and communicate whereas the whites started the war divided and were more spread out in the country, making communication much harder.
The term "Whites" is commonly referred to non-Red factions, and in fact there were White, Pink, and Green Armies all with different ideologies and plans. There were Ukrainian nationalists and different armies loyal to Imperial Russian commanders who sought to be the next leader Russia. One led by Admiral Kolchak tried to create his own country out in Eastern Russia, but that didn't work too well. Even the Allies, who landed up to 130k troops, couldn't decide on what to do in Russia.
Even the Reds weren't all that unified. Multiple Red provinces created their own Soviets that ideologically was allied with other Reds, but not operationally. What helped the Reds the most was that they were concentrated in the bigger cities in western and central Russia. If you read about how the Romanovs were transferred before they were killed, it was a risky process as they went through multiple checkpoints manned by different red factions of varying levels of support for the Reds.
The British sent in troops to fight Communism whil the US said its forces went in to free the Czechs in Siberia and secure hundreds of thousands of tons of supplies in Vladivostok. The Japanese went in and exploited Manchuria and parts of Siberia. Of all the anti-Red forces, I'd say the Czechoslovak Legion performed the best. They were being transferred to Vladivostok to be ferried back to Europe after Russia left the war (weird route, I know) and they stopped at the same station where some Austro-Hungarian POWs were being transferred back the opposite way. A brawl ensued, and the Russians tried to disarm and possibly imprison the Czechs. The Czechs were having none of it and seized the Trans-Siberian RR and multiple Siberian cities for the Whites until the Allies left.
The White Russian factions were splintered for good reason. The biggest being that different factions had different goals. Some factions were Monarchists, others were actually Mensheviks which was a similar communist group but had a different idea of revolution, one group was a bunch of Czech Soldiers that controlled part of the Trans-Siberian Railway which is a bit of a complicated thing.
The White Russians were really a bunch of different groups and that they were generalized and given the title as the White Russians. Meanwhile the Red Army was a unified force under the command of Trotsky and several other somewhat experienced commanders which ultimately won them the civil war.