Since 1976, only 2012 has seen the GOP select a candidate who didn't carry two out of the three early voting states of Iowa, New Hampshire, and South Carolina.
As they pointed out in 1988, no sitting vice-president since Martin Van Buren had been elected president...
First of all, of the eleven races since 1976, four--1976, 1984, 1992, 2004--involve incumbent GOP presidents. (True, Ford faced a serious challenge in 1976, but he was well ahead of Reagan in the polls; and of course GHW Bush was always well ahead of Buchanan in 1992.) A fifth, 2012, as you noted, was an exception to the "two out of three" rule: the party nominated Romney who (very narrowly) lost Iowa and decisively lost SC--he did win in NH, but after all he was from neighboring MA.
Of the remaining six, Reagan in 1980, GHW Bush in 1988 , Dole in 1996, GW Bush in 2000, McCain in 2008, and yes, Trump in 2016 could all be described as front-runners based on the polls of the previous several months--i.e.,
before any of these three early electoral events:
(1) Reagan in 1980:
https://www.nytimes.com/1979/11/25/...an-ahead-of-republican-nomination-rivals.html
(2) GHW Bush in 1988: "
1988: Vice President George H.W. Bush enjoyed strong front-runner status for his party's nomination throughout 1987. In January 1987, Bush led his most serious competitor, Dole, by 33% to 14%, and maintained a roughly 2-to-1 lead over Dole the rest of the year."
https://news.gallup.com/poll/146489/lack-gop-front-runner-2012-atypical.aspx
(3) Dole in 1996: "
1996: Bob Dole led former Vice President Dan Quayle 38% to 17% in February 1995. Then in April, after Quayle had removed himself from consideration, Gallup showed Dole leading second-place contender Phil Gramm 46% to 13%. And although Gallup's Republican test elections expanded to contain up to nine candidates, Dole faced no significant competition throughout 1995." Ibid.
(4) GW Bush in 2000: "
2000: George W. Bush dominated the potential Republican presidential field throughout 1999, leading Elizabeth Dole 42% to 22% in a January party preference test, by 52% to 20% in March, and by even wider margins later in the year until Dole dropped out in the fall. McCain ran second to Bush for the remainder of 1999, but continuously trailed by more than 3 to 1." Ibid.
(5) McCain in 2008: This may seem to be an exception in that Giuliani was the front-runner for much of 2007. But by January 2008, before the Iowa caucus, McCain had overtaken him in major states.
http://nomoremister.blogspot.com/2008/01/he-has-his-opponents-just-where-he.html
(6) Trump in 2016: I don't think it is necessary to point out here that Trump was leading in the polls for the GOP nomination all along (except for a brief period when Carson overtook him), however certain many pundits were that he would fade.
So I look at the fact that winners of the early GOP events usually go on to win the nomination differently from you. My view is that they won the early events because Republicans favored them, not that Republicans favored them because they won the early events.