History /
Where did the power of Poland vanish to, since... let`s say, some 300 years ago? [180]
I think it's a combination of many things. Liberum veto, which lead to parliament losing any sort of legislative or decisive power. The King and his crew were stripped of any power, too, so basically there was really no one to rule the country. The second big factor would be extremely conservative society and lack of any innovation, on any level of human activity (technological, constitutional, economical, military etc.) - Poles were merely followers, and even then they adapted innovations much later than everyone else. It basically wasn't a modern country anymore at the time
You cannot fight wars and survive as strong nation, the never ending conflicts Poland had to fight did it in, and do you see some nation following the footsteps of Poland with constant war, can we predict what will happen as history repeats it’s self.
Frequent wars weren't unheard of at the time, many countries had many ongoing wars.