Okay, Im confused. Why is this NOW on e621? I love the comic, but why is it now here when other places already have it posted?

because other sites post it before it is publicly released via patreon i'd guess.

artists get full custody of their work. its kinda a heckarooni because artists make stuff and give it to a large audience and out of those 10 people 1 gives it to a site and uploads it and it gets shared meaning the artist loses money, which is why artists watermarked stuff in the early 00s and now cause image sharing is way more frequent now they do far more obnoxious watermarks because of these half-pirates uploading paid art to free upload sites like e621. people dont like spending money on art but its a catch 22 because people see the watermark and remember the artist so they pay them. but at the same time the opposite spectrum give them no money because all their art is unconsentually uploaded to e621 or other sites so they dont HAVE to pay for it. kinda like stealing cable in america