In five thousand years of story telling only Beckett annd Chekov had the genius for both narrative and stage plays. Most writers fall short in one of the two, What makes the two forms so different that writers fail to excel equally at both.
A playwright is bound by limitations of space whereas a writer of narrative is free to travel the Universe and beyond. The world builidng is limited to what can be put up on the stage as set or props. For instance yiu never see the cherry trees in 'The Cherry Orchard'. Though the world and its visual images can be triggered by dialogues, literary techniques, auditory inputs, soundscapes and suggestions. A plate of cherries in an actor's hand can evoke the memory of a cherry orchard. This is the plasticity of stage that Shakesepare exploited to create housefull shows. On the other hand, the narrative writer can create multiple worlds with ease and at no cost. A skillfull playwright is not limited by space constraints, rather he engages the audience in the process of world re-creation.
A playwright is also limited by what his characters can say. The inner monologues of characters are never spoken, only hinted through acting, silences, pauses and light spots and shadows. Whereas, the power of narrative is in trasnporting the reader into the minds and hearts of characters.
Hence, writing for stage is a skill that is best learnt by working with actors and failing with your first few plays.