AFAIK ngrok was the first widespread implementation of it, and there was such a sheer lack of it before that everyone started working on their own implementations at once and now we have an abundance.
(At least that's my personal theory.)
Webhooks created the need for local tunneling software. Before ngrok, webhooks themselves were just starting to become more common. The need for local tunneling is much much greater than it was 15 years ago.
(Also consider that ngrok today is far more then a local tunnel proxy. They noticed the abundance of open source options years ago and have moved on from the basic concept.)
No, widespread means widespread. As in tons of people started to use it, ngrok started pivoting into enterprise, moved from ngrok.io to ngrok.com, etc. I was there for all of it.
The landscape of software other than ngrok was a total wasteland. Maybe there was localtunnel or SSH, I guess. But both of them kind of sucked and were fragile. ngrok was a static Go binary you could run anywhere to open a tunnel and it was total magic, worked perfectly, and was exactly what the world needed. It was the original. It taught people how this stuff ought to work and once people learned the formula, just like the iPhone, everyone else started copying it and now there are tons of implementations.