They weren't. The problem with the packets is that the beads are abrasive. And constructed for absorbtion of water, so they dry your insides, while injuring them. This is usually not fatal. Silica in a non abrasive form is just sand. Kids eat sand all the time without complaint. I know I did

If you're interested, ChubbyEmu details a case in which a man actually eats the silica packets. He gets hospitalised, but fares better than most of his stories www.youtube.com/watch?v=ChgI...

The dose makes the poison?

Not really, it's not toxic just abrasive, as explained my other comment. It's genuinely quite hard to be poisoned by silica