It's hardly a surprise. New EVs have been highly priced for the last many years and considered to be luxury or marketed towards the first mover market.
There has only been a tiny used market until now, so obviously availability can only increase which brings down the prices. Demand will tail behind because many first time buyers will be scared to buy used. It'll stabilise somewhere.
It's not a bad thing, unless you want to sell right now and buy new again.
When I switched to EV I did the calculations based on writing off the car entirely after 10 years. It'll probably last longer, but just to get the full depreciation into my calculations of whether it was worth switching at that time. The equations crossed after 6 years, so anything I could sell it for then would be profit in comparison to my car budget.
Anyway, my point is that the current value doesn't change my situation in any way. It was and is still a good deal for me to switch to EV. Gotta get on the train somewhere. Waiting for the market to adjust down to the sticker price on ICE cars is more expensive than worrying about resell value, unless you already know that you need to sell it again shortly.