Drugs and crime are related all right - and it is true enough that some part of that is because drug use in itself can in some cases make people more likely to commit some kind of crime (over and above drug use itself where this is illegal). This applies to legal drugs as well, most especially alcohol.

But prohibition njust diesn't work - it makes things far far worse.

The much more significant source of the link between drugs and crime is that prohibition directly encourages crime. Selling illegal drugs involves an enormous profit, and buying them requires an enormous expenditure, money which is obtained by crime of various kinds, and by selling on drugs and encouraging others to use them.

Take the money out of it, and you don't solve all the problems, but you would eliminate many of them, and get rid of the direct link between drug use and criminal activities.