About four months ago I watered my bonsai tree but it didn't soak in any water. Its leaves just hung. I changed its soil and removed all the rotten roots but nothing changed. Eventually, its leaves just dried out and became brown. They never fell off, they're stil hanging on the bonsai like that. The stem is completely firm and seems normal (as it seemed before this happened).
Is my bonsai tree still alive, and if it is, what should I do with it to help it live normally again?