Trusting startups to dispose of it properly if they go bankrupt seems like an absolute disaster waiting to happen. Netflix has/had an interesting series "radioactive emergency" based on real events that seems to be a fairly plausible outcome. The "Goiânia accident in Brazil occurred on September 13, 1987".
Trust isn’t a factor, regulations and DOE control are. You also seem to be really overestimating the amount of fissile material any one facility will have at any given time.
