You likely had soil that retained too much moisture, it's not at all uncommon to see succulents that appear healthy above ground, yet a sharp tug will reveal no roots at all, just like yours!
As long as the basal plate is intact they will grow fresh roots!
Letting them sit around, dry, for a few days or weeks would be good.
They need to scan over before they get into the dirt.
Setting them on top of the medium will work fine, or you can poke them in a little.
The main thing is to NOT water them for a while! Probably a month... Just keep plucking them out and checking for fresh roots, you can start watering again then.
