>>281693365
>He gave them a lot of blood which is why Nezuko became so strong
Exact opposite actually, he gave them a small amount of blood while he was tearing them apart, Nezuko got next to nothing and he thought she died like everyone else and just left.

To explain further, the reason he thought she died is the same reason why later he doesn't just explode her head, she's not connected to him like the other demons because she retained her humanity. Otherwise he could control her mind or make her suicide.

The reason she's so freakishly strong is the same reason Muzan's strong and why Tanjiro is a goddamn nuclear warhead who would be even stronger than Muzan when he becomes a demon, they both got exposed to the same flower that turned Muzan into a demon, but they didn't inject a half-baked formula into themselves. It's growing on the grave of Yorichi's wife, not directly stated but likely because she had it as a medicine when she was sick while pregnant.