It's not because of the break, it just depends if someone can find it (and buy it), it's not everytime the same plateform that leak it (here it was Amazon), but everyweek WSM simulpub chapters leak (you can see it with Edens Zero which leaks everyweek for 2 years now)
35 796 sales with only 3 days is a good start.
It's one of the best start for a series in WSM since a long time
It will probably reach 80k~ sales next week
Ofc it could have been better because it's Nakaba, but that's still good (and it's not comparable at all to Samurai 8 failure)