It's not messed up. Well, not always. When you talk about intent, you're confusing conviction and sentencing.
Consider drink driving. If you get pulled over and blow over the limit, it's not exactly crime of the century. If you're drunk and you run over a pedestrian, it's a far more serious matter. Having said that, there are plenty of examples of habitual drunk drivers receiving custodial sentences, while a first time offender who runs someone over escapes jail.
Sentencing has to consider culpability, the prospect of rehabilitation, the rights of the victims, the need to protect society, and a range of other factors. It's not uncommon for an attempted murder to attract a more severe punishment than an actual murder.