I'm not a financial wizard by any means, but IMHO we had a perfect storm of contributing factors. First, we had a booming economy for several years prior to Covid. Most folks (granted not all) saw meaningful gains in their net worth, as well as discretionary income. Throw Covid into the mix and that put a serious kink in the supply chain. A boat is obviously a combination of hundreds of components from different sources, and when those sources either cut production or shut down, even for a short time, companies that used just-in-time inventory management didn't have the stock on hand to complete boats. Many builders either closed or reduced production due to staffing issues.
Lots of folks got bored, frustrated even, with the situation of being masked up, being told where they could eat (carry out only vs. dine-in, work from home, etc.) Enough folks decided that it was time to scratch their boat itch that might have been festering for a long time. As the saying goes, "If not now, when?"
As always, folks chose both new and used boats. Given that most (if not all) boats are a compromise, folks probably settled for what they could get. If they couldn't get a new model in less than X months and a used one was sitting on the lot, well, instant gratification won out.
It will be a very slow process to fill backlog and return to pre-pandemic production. My guess is that it will look like we're back in 2 years, maybe sooner... unless new pandemic restrictions are implemented. Then all bets are off. Suppliers are still facing staffing shortages, as are builders. Lots of boats have been pre-sold and it will take six months to a year at least to fill those orders If and WHEN builders can get the supplies.