A bit of an over-simplification in my opinion.
The demise of magazines in all genres is down to rising production costs and that they are not the only medium any more - as has been said on this forum many times, there is so much great content on web-sites and forums (fora?), discussion groups, etc. these days that has largely replaced magazine content. I personally still enjoy printed content more for my core interests (e.g. line Society journal and G3 Society newsletter) but the national mags have had little appeal for quite a while now (model railways and model engineering). I wouldn't be surprised if advertisement income for the national mags is also reduced as most traders have a high reliance on their own web presence, and magazine advertising doesn't show any benefit.
The
Midlands Model Engineering Exhibition is still going strong. As I recall, it started as a more northern alternative to the London-centric MEE (Wembley, Central Hall, etc). and was variously held in Birmingham, Stoneleigh etc before TEE publishing / Meridienne Exhibitions got their own premises at The Fosse. Rising costs have been a key challenge for Model Engineering exhibitions too. Before the internet, the only way to sell machine tools was to lug a few tons of them around the country and the shows were full of shiny new machines and a good range of used too - so people came with wallets full of cash as it was the only opportunity to 'shop around'. All that = healthy stand fee income for the organisers and traders making a profit. The traders can no longer make a profit doing that, as they sell much more through other means and it is disruptive to normal operations, stock control, etc.. The knock-on effect to the exhibition organisers is obvious.