What if the Mensheviks are not betrayed by the Bolsheviks during the Revolution or better yet...
what if they don't split in 1905?
They split over deep disagreements about fundamental doctrinal and strategic issues; it's implausible that either side would not evolve under the circumstances, or that partisans of one or the other would simply defer to the other side.
It's not implausible that individuals from one side would gravitate to the other as circumstances changed--Trotsky was a Menshevik until mid-1917 when he became impressed with what he saw as the correctness of Lenin's approach and joined the Bolsheviks. Going the other way--the Bolsheviks certainly accused many of their members of deviating in all directions, including rightward, which is where they placed the Mensheviks.
The best-developed timeline I've seen that considers the possibility of an ongoing tactical alliance of the Bolsheviks with not only Mensheviks but the agrarian Social Revolutionaries and even tolerance of certain non-socialist parties has been LordInsane's
A Central East. Frankly I don't think he did a whole lot of homework to show just how and why someone like Lenin and his close followers would compromise and learn to continue to compromise like that; I just accepted that that's the way it was in his timeline.
A plausible reason was that ITTL, Germany was in a much stronger position, militarily, politically, and even morally, than OTL, and won WWI much sooner, being able to inflict a crushing defeat on Tsarist Russia a year earlier than OTL; revolution in St Petersburg and in Russia generally did follow, but arguably the fact that it happened after a year less of general bloodletting meant that Lenin would calculate his position was not as strong as it was when he returned OTL; he might feel forced to accept tactical cooperation with other groups who would be less weak than OTL; this might explain the much more legal, parliamentary route the Bolsheviks take ITTL. Also there is a civil war, but like the Great War ITTL, it is shorter and the carnage is much less than OTL--in terms of body count; in territorial terms the "Red" core of Russia (never called Soviet here though I think LI accepted my reminder there would be soviets) is much reduced. But I gather in not only human but infrastructural terms it is a lot less devastated. So on one hand the rump of Russia is better able to rebuild from a higher level, including people who OTL were killed or fled, but on the other these people are often "class enemies" in Leninist terms--but Lenin can't just kick them out or kill them, he has to either leave himself, the Bolsheviks generally resigning from politics, or work more or less with them at least for now. Hence the much less radical and broader Russian revolutionary process--which is however still alarmingly radical from a Western bourgeois point of view!
In the situation OTL, the Leninists did not see the need to work with a broader coalition for the most part, and I suspect they were right to fear the risks of trying to do so. Change the circumstances and you might get a more cuddly Lenin! But make no mistake, the man was quite sure of himself and of the desirability, from his point of view indeed the necessity, of making sweeping changes in the order of things and had no doubt that this would make him legions of enemies, not just among outspoken reactionaries, but among other leftists with different prescriptions.
I might be wrong about this, but I doubt the Bolsheviks were the only ones in this mix who were intolerant and arrogant and quite willing to dispose of all rivals at the first chance. In the end I attribute the Bolshevik triumph to having won over the loyalty of industrial workers, when they considered the nature of the alternative leadership available. In LordInsane's timeline, other factions were strong enough and the workers could be placated enough that Lenin could not overplay this hand; OTL it wound up being IMHO the only hand on which to base a Russia both independent of foreign influence and with prospects of development, and for that reason in the end a lot of former reactionaries who had had no pretensions to being socialists or even democrats came over to their side, as the heirs of Russian patriotism.
Feel free to imagine other paths to a more collaborative Bolshevik party; I just disbelieve it could emerge from the situation as of 1917, OTL. I invite anyone to show me how that presumption of mine is wrong!
