Most issues are caused by concommittant alcohol use, since it makes cocaine metabolize into cocaethylene (ethylcocaine), which is both more addictive and much worse for the heart.

Quoth Wikipedia: Some studies suggest that consuming alcohol in combination with cocaine may be more cardiotoxic than cocaine and "it also carries an 18 to 25 fold increase over cocaine alone in risk of immediate death".

Interesting. That’s pretty much most popular combination.

People die from cocaine even now when it's illegal. The question is if harm would increase due to legalisation. I think there is a good argument that harm could actually be reduced since quality and dose control would be much better. Treatment is also easier when those with substance use disorder are not seen as criminals.

Maybe if you sold in fairly limited doses in pharmacy by prescription at which point it would loose fun and create another market for aggregators/resellers. It's not like weed where it's impossible to OD (tho it can be very stressful).

People generally don't want to overdose. ODs happen when people are mistaken about the quality and purity of the product they get hold of. Legalisation would reduce the risks significantly.