It's a nice cliche (perhaps influenced by great TSK made by
@Augenis) but no, Orthodoxization of Lithuania proper wasn't that easy. Of course, a lot of Lithuanian princes converted to Orthodoxy when ruling minor Ruthenian principalities, but they were usually stripped from their rights to succesion - all sons of Algirdas from his first marriage were banned from becoming great princes, and Jogaila didn't want to accept Orthodoxy and broke his treaty with Dimitr of Moscow for reasons. Also, when Gediminas tried to place Orthodox Jaunutis on the throne, Algirdas and Kęstutis gained a lot of following among Lithuanian nobility. Lithuanians saw Orthodoxy (apart from royalty) as a religion of weak, easily conquered men, so not suitable to spread in Lithuania proper. Lithuania would most probably stay pagan for a century longer, and then I don't know what.