I happened to speak to a few big exhibitors last week (inc big mobo outfit) and I suspect they somewhat took the decision away from the organisers It's one thing setting up an electronics stand, quite another getting a significant range of large boats in the right place at the right time, sending marketing material out to potential owners, organising hospitality, etc. Then there is the problem that many potential customers will no longer travel.
I suspect the decision has been half taken for some time and it is certainly a far better option than running a damp squib show.