To my memory, people had been using [link](url) and similar styling for a long time on old web forums and even BBSes.
Be glad they didn’t adopt Everything2’s “pipe link” syntax: [link|url]. Or maybe it was [url|link]? It’s been well over two decades, I don’t remember anymore.
I have never heard of [text](url) being used before Markdown. “text (url)” or “text <url>”, leaving the reader to infer which words the URL applied to, sure; but among formats that provided a span for the link text, I think Markdown may have been the first to use a spelling of two adjacent delimited parts. [urltext], [text|url], [url="url"]text[/url], et cetera, seen them all.
Be glad they didn’t adopt Everything2’s “pipe link” syntax: [link|url]. Or maybe it was [url|link]? It’s been well over two decades, I don’t remember anymore.