Were there one million people, or anything remotely close to that, stood on the steps of Lime Street Station at any point? I wasn’t there so can’t say for certain, but I’d assume the answer be no.
The more manageable thousands of people however still couldn’t get on the trains that likely could’ve supported them albeit queues until the end of service, and a far smaller pool at the end of the service scrambling for Ubers.
Only if the trains had been allowed to fill up can we question whether the system could cope or whether there was enough provision and accurate passenger estimates. But that didn’t happen.
No, obviously there weren't 1,000,000 queuing on the steps of Lime Street.
But if 1,000,000 people are attending an event in a city with a population of ~500,000 then that means at least 500,000 have travelled into, and will be travelling out of, the city. Realistically, every single resident of the city of Liverpool will not have attended the parade, so that number of people travelling in and out of the city proper will be closer to 700,000 or more. Again, obviously, not all of those 700,000 will be long distance travellers, a good proportion will be from Merseyside. The population of Merseyside is ~1.5 million. If you take away the city population, that leaves 1,000,000 for the rest of Merseyside. Clearly, not all of the 700,000 simply travelled from other parts of Merseyside into Liverpool, and even some of those that were would have been using Lime Street. Given all that, I reckon you're easily talking a couple of hundred thousand people from outside the area - and easily a number of people trying to use Lime Street that far exceeds any standard event day crowd control measures.