We can go through the primary:
en.wikipedia.org
en.wikipedia.org
Trump did gain traction in the early elections, but in Super Tuesday and between the super Tuesdays, he didnt even very decisively outpace Cruz. Had Kasich and Rubio fallen in line here and given Cruz their endorsement like Buttigieg, Klobuchar and so on did, the moderates would have consolidated behind Cruz. If Cruz had won super tuesday and some primaries after that decisively, the Trump hype would quickly have died down.
Trump was not very dominant in the primary. He was less dominant than Biden in his, even tho Biden was hardly a phenomenon. He would never have won had the republicans done what the democrats did before the first super tuesday.
Trump runs on hype. Losing super tuesday decisively (which would have happened, he already only won rather closely) would have ended his run.