As the title says, why did my duck legs shrink so much after the first day?

Duck confit is my favorite French dish, so I always wanted to try making it at home. I used Bruno Albouze's duck confit recipe, which can be found on YouTube. This meant slow cooking the duck in duck fat at 275 for 3 hours, letting it rest at room temperature, and then searing each side just before serving. The top picture is the final result after I followed these steps on Day 1 of cooking this dish.

Bruno Albouze said we can store duck legs up to 2 months by submerging them in duck fat and storing them in the fridge. Then microwave at low heat to turn the duck fat from solid into liquid, and then sear each side for a few minutes just before serving.

Image of the dish here: https://ibb.co/Nt40qXK

I followed these exact directions, but you can see that the duck legs I made 2 days later (as seen on the bottom pic) are much more dehydrated and shrunken and not as visually appealing as the top pic. The meat was also slightly tougher on Day 3 as well.

I have heard that duck confit is one of those dishes that get better over time, so what did I do wrong? Is there any way to prevent this from happening again? Do I need to slow cook at a lower temperature on Day 1? I have a new oven, so maybe it’s hotter than older ovens?