Actually it doesn’t seem ludicrous to me at all. State amendments, local issues, often drive voting blocks out to vote, and hence influence the national election. It works both ways too. An example is the idea that in 2008, large turnout of black voters, inspired by Obama to make it to the polls, whom also happen to be statistically more religious than average, rejected the California gay marriage legalization amendment.
But frankly, the two issues of medical marijuana usage and nuclear weapon control are not ludicrously unrelated either. The question of medical marijuana is one of belief in individual rights of Americans, of protection against clear government tyranny, of putting an end to violent, racially discriminatory wars on normal people. When I think of whom I want controlling the nukes, the first characteristic I think of would be respect for humanity. Anyone who can’t respect an American’s individual right to a life free of of tax payer based government harassment certainly shouldn’t have a chance at using weapons which serve no militaristic purpose in our current world.