>>/8995/
It wasn't wrong as you can see it was pretty safe business considering. Well up until cannons started peppering them.
For the minds of the rulers like Friedrich the Great or Napoleon and the generals of the era the musket infantry was just pikemen with extremely long pikes. They thought them as such and used them as such. This is why the musketeers took over the place of the pikemen in the pike and shot formations (after the adaptation of bayonet), pikes are nice but we can reach farther with muskets.
The evolution of the artillery and the appearance of rapid firing infantry weapons were the cause which forced the infantry behind cover, barricades and finally into trenches.
>>/8987/
> swords gradually got more curved with time
This would be right if we could see how the Japanese swords evolved from straight to the point when it's a circle. But there's no such pattern. If you pick a decade and hoard all the swords made in that decade you would see curvatures of all degree. Swordsmiths shaped their swords as they preferred.