I don't actually think the short forms were planned? People are assuming that they were but I think that what happened was simply that North Staffordshire line services were protected at the expense of everyone else. Given the size of the crowds it's unclear what else EMR were to do.Not quite sure why it should be considered acceptable to short form a key (and by all accounts, and personal experience, very busy) timetabled flow (Nottingham - Liverpool) to provide extra capacity for "occasional" passengers wishing to watch a horse race in Uttoxeter.
For example at the Lincoln Christmas Market Northern withdrew their services from Retford to Cleethorpes via Brigg and diverted them to Lincoln instead as a way to provide additional capacity. This naturally prompted furious backlash from the affected towns who had rail replacement buses. But what else can be done? In my view it makes some sense to withdraw less used services when there's a major event on. SWR withdrew their services to Dorking when the Royal Wedding was on to provide more capacity for Windsor trains for example.