I don’t think scale will cause the element to draw too much power. resistive heating elements only pull one value of current (unless they have some kind of rheostat control like a stove burner).
I guess it’s possible that scale caused the burner to be less efficient and not able to dissipate the heat produced tho.
It’s more likely the connector started getting loose and that caused a high resistance connection right at the connector and burned the connector up.
But it’s hard to know for sure without looking at it more closely.