Considering that they can move the whole house, they practically camp small army everywhere on the frontline and use those houses as temporary super deluxe base, with even 24/7 surveillance available.
The 3 heroes all died during their previous life because of their bad personalities.
Being reincarnated with superpowers certainly didn't help.
As long they think they are invincible they will cause countless victims everywhere
That's the why. He found out a easy way to make money and used his broken niece to do it.
Now that he doesn't need her anymore he discarded her like a used tissue