Why did this element burn out?

[Camo6]

This is the plug and cable that came out of it so i dont think the wire gauge was the problem. If its wired around the wrong way I wouldnt know. I thought it didnt matter with elements but apperently thats not the case.

Anyone need a 3 phase male plug?

The element is a resistive load so polarity won't matter. Correct cable identification is important from a safety perspective but having another look at your pic I notice the red is already disconnected so my earlier assumption is probably incorrect. The connections in the plug top would confirm either way.
The insulation failure is likely due to heat caused by either excessive resistance in the terminal or element, or the cable not being rated for the current draw. It looks like 2.5mm2 orange circ which should carry the 23A without trouble although it really should have been wired with flex.
The fact that the screw is rusted is a sure sign of high resistance likely due to water ingress. I'd chuck the element.

 

[Bonenose]

High resistance joint is spot on, no issue with polarity or anything along those lines simple case of the neutral joint being the dodgy joint therefore it heats up and melts the insulation. Heating will be localised to the bad joint so will not be evidence of overheating on the active.

 

[S.E]

Without proper testing this becomes a dangerous guessing game. I think talking about the electrical side is against forum guidelines anyway. Im in aspendale if you want someone to check it out. I wont even charge.

Talking about electrical side is not against forum rules and dangerous guessing games is in fact what
[SIZE=11pt]the forum was built on. [/SIZE] If you are in the Op area this could be sensible and generous offer though.

 

[nosco]

The best advice I got was to throw it out, which I have. It wasnt easy but I did.

 

[S.E]

The best advice I got was to throw it out, which I have. It wasnt easy but I did.

What did you throw out,, the element or whole brew pot?

 

[peteru]

As always, the underlying issue would have been not enough lube.

 

[nosco]

What did you throw out,, the element or whole brew pot?

Just the element. Selling the pot and the plug in buy and sell thread.