WS,
"... there is no one 'media'. Thus, 'the media' can't do anything or have any preferences."
Can the "electorate" do something, or have a preference, even though there is no one "elector"?
"But those who were liberals probably had no real preference, because they were all pretty bad, from a liberal's perspective.

Carson, Perry, Huckabee, Trump, Cruz--they all turned my stomach, one just as bad as the other. I can't imagine that 'the media' would settle on any one of them as the best. Maybe Kasich, Rubio or Bush, if they had to choose."
I am suggesting something a little more cynical. Who, among the original seventeen candidate Republican lineup, would be the most
useful as a foil against the other sixteen? I understand that the candidates mentioned are equally reprehensible to you.
They were also more viable in the general election... especially, as you point out, Carly Fiorina. With her poll numbers rising against Trump, who then stood at 32%, why did Paul Solotaroff of Rolling Stone decide to take a comment made about Fiorina's face in the isolation of Trump's 757, and give it world-wide air play? Was it an attack on Trump, or denigration of Mrs. Fiorina via surrogate? Solotaroff characterized Trump a few days later as an "extraordinarily shrewd predator". I think Solotaroff appreciates the corrosive nature of dangling ad hominem. His time at the Yale School of Drama appears to have cultivated some sophisticated predatory rhetoric in his own right, but not much in the way of professional journalistic discipline.
"The very things that would make him the most likely to lose would be the things that would make him most likely not to be nominated."
Not in a field where three of the four outsiders (Carson, Fiorina, and Cruz) were competing for the same voters while Reagan Democrats consolidated under Trump.
"If they saw him as being a horrid candidate, why would they think the Republicans wouldn't notice those things?"
They knew conservatives had identified Trump for what he was without their help.
https://www.google.com/search?q=national+review+cover+trump&ie=UTF-8&oe=UTF-8&hl=en-au&client=safari#imgrc=5kz_Fp1idifzHM%3A The objective was intra-party fratricide, leaving the single ideologically-void candidate standing.
"Why would they discuss how he is a bully if they thought it would 'turn on' the Republicans?"
Because the Yellow Dog, and Rust-Belt, Reagan Democrats needed to be brought in line. Bill Clinton understood this very well.
https://www.google.com/amp/s/wlwt.relaymedia.com/amp/article/bill-clinton-speaks-at-labor-day-picnic-in-cincinnati/3613258?client=safari" 'The media' may have had its preferences, and may have hoped that Trump was the one candidate who would lose, but by showing Trump to be the clown that he is, they could not have expected him to win the nomination because of it. If they believed Trump wasn't good enough to win the election, he shouldn't have been good enough to win the nomination."
No, one condition does not logically follow the other. Every election cycle there is a candidate good enough to win their parties nomination, yet lose the general election.