Your question is deliberately skewed in a manner to deflect moral responsibility; better to ask what sort of person enters into a career path upon which he will knowingly abet the degradation of society by doing his utmost to keep social predators out of prison? The answer, IMO, is a person with a broken moral compass, for whom money in substantial sums acts as a lubricant for the long slide into acceptance of petty niggling over legalisms as an expression of his contempt for justice and cynical disregard for the pains of criminals’ victims. Not all lawyers are moral degenerates, of course; there are always fine people in any profession. It’s just that a great many are ever ready to subvert justice by deliberately coming to the defense of the indefensible - for a buck.
Right. Explain public defenders, then.