Naw, it was firearms that ended the use of plate armor, starting with Gustavus Adolphus's heavy infantry, who would actually discard their breastplates if issued them. By the Napoleonic era, most "cuirassiers" were nothing of the sort.
Thats a common but wrong misconception.
Guns and plate armor existed side by side for several centuries and they were made bullet proof. Also the downfall of plate armor was not (only) because of guns but also because of pikes, which replaced knights on the battlefield, and the high cost of them in a time where the size of armies increased a lot.
That the Swedish infantry dismissed their armor was likely more do to Adolphus himself refusing to wear armor trusting instead in faith to protect him. The result was a bullet in the shoulder which caused permanent damage.
Just about every weird, wacky configuration of stick and sharp metal has been tried historically. Typically you'll find that the weapons that are used the longest and most effectively are those that offer long-range stabbiness or close-range cuttiness or choppiness. This is a guideline, not a rule, mind you, and lasts only until the age of gunpowder. Foot lance had its last hurrah in the tercios of the 30 years war. After that, all reach weapons were either mounted lance or guns on foot.
You make it sound like weapon usage was pretty much random which is far from the truth (Except for maybe peasants who had no access to real weapons).
Creating weapons was a science as much as creating armor and as the Jester said they were in constant competition against each other. Armor was designed to stop the common weapons of the time and weapons were created to penetrate the armor people wore.
And you are wrong about lances. While the 30 year war was the last high point of tis weapon, pikes were still used till the 17th, in some cases 18th century (Sweden and Russia).