Considering they’re going for patent infringement and not copyright infringement, it’s possible it just took this long for Nintendo’s legal department to find something even remotely tangible that they could sue over. And since they haven’t said what patents Palworld infringes on, I have to assume whatever it is, is very flimsy.
“Align your chakras, warm up your crystals, pray for the summer and winter solstices, wait until the stars and planets are aligned but Mercury is also in retrograde…”