Brooks and Moore split the conservative vote, to Strange's benefit. Both strongly opposed McConnell, and true to form, McConnell gave his backing and boatloads of money to the establishment candidate, Strange.
McConnell wages war down South
Strange was endorsed by Trump, Pence, and McConnell. Say what you will about Moore, but either Moore or Brooks would have been a much better choice than Strange who is a corrupt swamp creature. The stench of corruption that hovered around Strange would have been heavily exploited by Jones, and Strange would probably have lost, in spite of the conventional wisdom that he was a shoo-in.
Strange was one of Trump's worst endorsements. Let's hope he is getting better advice this time.
As I recall, there were a lot of posts here on FR back in 2017 from Alabama Freepers who suggested that Mo Brooks was only in that race to undermine Roy Moore and give Strange the nomination.