Why zero delegates?
Because of rules agreed to by both major parties, all but a few states will be penalized by a reduction in national convention delegates if they hold their primaries before March 1. By law, Missouri's is in February; the state legislature didn't approve a move of the primary to March (another series of bungles), so the state Republican Party had to call for and approve caucuses. Hence, the March 17 caucuses will choose the state's delegates to the national convention.
The February 7 primary is a very expensive beauty contest - straw poll - and nothing more. The results that matter will come during the March 17 caucuses.