https://www.washingtonpost.com/graphics/politics/2016-election/primaries/explaining-the-presidential-primary-process/
Republican states catered to the winner take all system and front runners after the delegates appropriated to candidates are not proportional to the amount of votes they received. This was especially seen in later primaries where they rewarded the front runner (Donald Trump) in his success and allocated more delegates to him then what was proportional from the votes he received. This article also gives a breakdown of the states and how they allocate delegates based on votes.