Even though Moritz is interested in seeing what an Olyphant-led The Fast and the Furious would have looked like, he can’t imagine anyone other than Diesel as Dom in the actual series.
Neal Moritz then added during his interview on The Bill Simmons Podcast that after Timothy Olyphant passed on appearing in The Fast and the Furious, Moritz went to key folks at Universal and suggested Vin Diesel for Dom Toretto, who by that point had appeared in movies like Saving Private Ryan, Pitch Black and The Iron Giant.
Moritz then added that had Diesel not accepted the role, he doesn’t think the movie would have ever made the movie.
Fortunately for Moritz, both the studio and Diesel were game for this choice, and the rest is history.