Crown was smaller then Lithuania. I don't know exact numbers of land so just example:
Doesnt matter it had more than ten times the population and was more than 300 years ahead in military technology.
Apart from the fact that Lithuania had a tiny population another fact is omitted, these guys were technologically at about 12 century level, they didnt have heavy cavalry in the true sense, they didnt use or know how to produce plate armor and unlike the Scots a pike was an unknown weapon to them. at the time of the union Lithuania didnt have even one stone castle, thats how huge the difference was
After the Battle of Grunwald king Jagiełło had to delegate a thousand polish knights just to escort the lithuanian army back home.
The Piasts were also responsible for the fragmentation of Poland
True but you have to remember that back than nations didnt exist, also its the Silesian Piasts that are responsible for elevating Poland back from its fragmentation and into power.