Why did unified Spain use Castilian instead of Aragonese or even Astur-Leonese Spanish as the unified language for the peninsula?

by larkspurblossom
jja2850a

This post by u/itsalrighrwithme may answer your question: https://www.reddit.com/r/AskHistorians/comments/6iqusl/why_did_castilian_become_the_default_spanish/?ref=search_posts