Poland was the stronger one in the union.
Please, be so kind, and point me to the part of my post where I said Lithuania was stronger than Poland?
You are operating in complete fantasy land. Who would let you take the crown of Bohemia - which was firmly attached to the Holy Roman Empire and the Habsburgs specifically?
Your so-called nobles, approached Jogaila - exactly because they did not want to end up under some inbred Austrian - who they felt would trample over their rights. The Lithuanians, in turn, were actually amenable to being swallowed up by you, because they were mortally afraid of us.
This was the perfect marriage of convenience. Poland avoids becoming some personal Union under a Hungarian/Austrian center, while Lithuania avoids being smashed by Russia. Nobody else, would merge with Poland, as willingly, as bloodlessly, and for such a long time.
With them, you did not acquire some small bunch of forest dwelling Samogitians, but the original Lithuanians. The good Lithuanians. Millions of future Belarusians and yes, even some future Ukrainians.
Instead of being grateful for this magical moment of Polish history, you are here telling me you would rather be tongue kissing some Czech. Very nice!