I don't buy it. I was not so bold as to confidently predict a Trump victory, I did, however, throughout the campaign, tell friends that she was not, as our fake lying news said, a prohibitive front runner. I had no special insight into the inner workings of the Clinton campaign, I didn't need any to know that her campaign had trouble from the start.
1. The ninth-year curse. Since WWII the history of the presidency has been eight years of a Republican in the White House (1953-1961), followed by eight years of a Democrat (1961-1969), followed by eight years of a Republican (1969-1977). The pattern was broken by Carter who served but one failed term and Reagan/Bush with 12 years of Republican presidency. After that we reverted to pattern with eight years of a Democrat (1993-2001) and eight years of a Republican (2001-2009). All other things being equal we should have expected eight years of Obama to be followed by a Republican. The lying mainstream press insisted that Clinton had the advantage because she was of the same party as the popular incumbent. They conveniently ignored that in 1960 Nixon, VP to popular incumbent Eisenhower, could not overcome the ninth-year curse any more than Gore in 2000 could turn Bill Clinton's popularity into a victory in the ninth year. Her party registration was, from the very beginning, a liability, not the asset that the press said it was.
2. The lying mainstream press repeated that she was consistently ahead in the polls and had an insurmountable advantage. In fact, to my knowledge, there was no reputable poll that indicated that. The polls showed a slight lead, so small that a true account would have reported it as neck-and-neck. Further, there was one extremely telling number. Clinton never got above 49% in the polls, with Trump trailing slightly in the mid-40s. Clinton was not the incumbent, but she was running as if she were the incumbent seeking a third term. One rule of thumb, that anyone who follows political races knows, is that, in a two-way race, if the incumbent is polling at below 50%, the challenger will win. You learn this in "Campaign 101," undecideds break for the challenger.
3. Related to #2 was the fact that Clinton, by one important measure, was one of the most qualified persons to run for president. As former first lady, senator, and secretary of state she had ample Washington experience and universal name recognition. Yet, with all that going for her she could not get above 49% in the polls in a race against someone who had never held public office and was prone to intemperate utterances not typical of someone seeking the most powerful job on the planet. It didn't take a tell-all-book after the fact to tell me that her candidacy was in trouble.