Although the organization claimed to be in business for many years, the domain was only recently registered. And at the dates they mentioned there wasn't an exhibition of that kind planned in the exhibition center they mentioned.
To be fair, I can see a legit (albeit sloppy) company doing this. In fact, almost the exact same scenario happened to a former client.
They had an existing site for many years, running the same travel trade show at the same venue each year. After we stopped working with them, they stupidly forgot to renew the domain name (which got snapped up by a squatter), so they had to register a new domain name. (Note- even though they were no longer our client, we actually sent half a dozen messages to them reminding them to renew, but their new consultant never got around to it.) When they updated the content (their new consultant also was not fluent in English), the low-level/low-paid person changed the years for the dates, but not the actual months/days of the event. That year's trade show was moved up 1 month because of a scheduling conflict. Also, they had no real competition, so no other place from where they could scrape data.
So in their case, the red flags of spelling mistakes, recent domain registration, and incorrect dates were just indications of sloppy work, not any attempt to defraud. My guess is that all the companies who paid were advised of the correct show dates.
However, given the red flags, I completely agree with your assessment that additional investigation was certainly needed.