Because that's how the author chose to write it. Because that's where the audience they write for is. Because they prefer Twitter threads to blog posts. Beca

Because that's how the author chose to write it. Because that's where the audience they write for is. Because they prefer Twitter threads to blog posts. Because they get more readers that way. (And probably anyone here can come up with some more reasons that might be true if they put their minds to it.) But mostly, the format someone chooses to make this available in is the least interesting thing about it.