Looking at the Internet Archive for typescriptlang.org, most (but not all) of their original samples are doing something in a browser[0], so while it definitely became popular with backend developers, I don't know if I would go so far as to say it was created for non-frontend developers who were forced to deal with the frontend.
Out of curiosity, is Monarch using Plaid for financial data aggregation? I have been wondering how long it would take for a standalone budget/asset tracker to emerge using Plaid's services. It seems most Plaid users are selling other financial products, and tack on aggregation as an additional feature, like Personal Capital.
[0] https://web.archive.org/web/20121004030106/http://www.typesc...