21. The Resistance did not actually win the war
In “The Rise of Skywalker,” the Resistance is able to destroy Emperor Palpatine’s fleet and one First Order Star Destroyer in the last war. So, as a result, the rest of the First Order’s military is still out there. And according to various sources, the First Order has amassed enough forces that it conquered the entire galaxy in a few days.
Which means that, even with the mob of randoms they created in this film still, the Resistance has a long road ahead of it if it wishes to free Galaxy. So to put it another way: when we see random Star Destroyers getting destroyed in the epilogue of “The Rise of Skywalker,” the entire war happens. Yikes!