People with poor risk management skills probably serve some useful purpose because we still have them, but they are not the cause of all human progress.
Specifically:
We’d still be living naked in the savanna if it weren’t for people like this.
Processing skins of kills has nothing to do with risk taking behavior, nor do the host of incremental adjustments that lead from skinning to tailored clothing.
Similarly our expansion into areas beyond the savannah has nothing to do with unnecessary risk taking, it's just the result of favourable conditions that increased the birth rate.
floated off to sea... They settled lands
Permanent human settlements aren't founded by rugged loners washing up on a new shore. It takes at minimum ~20 people and new sites are scouted well in advance to make sure they have sufficient resources to support a growing population.