Are elves stupid ?

[Rune Son of Bjarne]

or maybe just careless?

Why did the elves not find wayes to defeat Glaurung?

Glaurung first apears two hundred years before the Dagor Bragollach, but is driven off by Fingon and thoug the elves at this occasion has been pree warned, they were unable, to contrive means to deal with beasts of his sort.
Again in the Nirnaeth Arnoediad, he slayed many men and elves before the dwaves drove him off the battlefield. This showed that comprehensive body-armour was able to withstand the heat and flame of Glaurung.

Why did the elves not prepare for Glaurung after there first encounter? were they over confident or did they just don't think about it. (this is very hard to belive)

Why did the elves not use body-armour of the sort the dwarves used? foolish pride or . . .

Please give me your thoughts on this subject.