Originally, Hussars had "heavy" (e.g. Polish) cavalry, and "light" (e.g. Hungarian) cavalry side by side. So then the question is what tipped the balance in favor of "light?"
The answer I have is terrain. Poland (and Russia) has mostly flat land. This is ideal for the charges of heavily armed and armored horsemen over "easy" ground, for massed, line-breaking charges. As the Poles and Soviets unfortunately found out during World War II, most of this territory (except the Pripet Marshes of the Ukraine, and the Byelorussian forests) was good "tank" country. Heavy cavalry tactics worked well enough at the Battle of Vienna, 1683.
In the south, the situation was different. Hungarians facing the Turks invading from the Balkans operated over hillier, forested ground, better for light cavalry. Here, the emphasis was not on massed charges, but reconnaissance and "blocking" actions by faster, more lightly armed cavalry.
Western Europe had more "Hungarian" type (hilly and forested) than "Polish" territory. Hence light cavalry was more suitable, especially since the introduction of firearms foreshadowed the vulnerabilities of (French) heavy cavalry at battles like Crecy, Poitiers, and Agincourt. Western European cavalry moved closer to the (lighter) Hungarian model, eventually veering into "dragoons"(mounted infantry).
The 1683 Battle of Vienna was the "last hurrah" of heavy cavalry. Thereafter, cavalry got "lighter and lighter" as firearms got better and better beginning the end of the 17th century.