Follow the money -- where did it go (and where did it not go)
In the same way that it is not sensible to dope a horse, and then not bet to take financial advantage, it is not sensible to pull a horse one day before letting it go on another day, without playing a financial hand.
Evidence of such behaviour would be in the betting market in terms of 'firming' and 'easing'- - usually too late for TAB punters to change their bets
The evidence would also be in the betting behaviour of 'connections' : this evidence is apparently never found presumably because it is never looked for and that is an indictment of the administration of an industry noisily claiming a commitment to integrity.
............. there is not much integrity in a Cup week being Xmas for bookmakers......... but that absence is compensated by contriving a controversy about possible misbehaviour and a flurrry of noise about what will be done to find and punish it.