what's unknown are what the ACTUAL numbers were from prior years. when I shopped on onlyinboards in the past there were always quite a bit of ads that had been put up and never taken down. it doesn't appear that ian cleans house much on there but more relies on the seller to remove ads.
my gut is as covid started and boat sales took off, people were calling the old ads on a hope that they were still available which prompted people to remove them.

I suspect that there were never really over 5000 ads "active" in years past. go to the last page and there's some steals from early 2020 that I would bet money are not still for sale from that owner. still a hot market for sure....