Yes, the beta version of 2017 added file imports and more Last.FM compatible options, as well as announcing that:
We don’t plan to reset the database from here on out — this is the real deal and we plan to safeguard and make this database available as soon as we can. If you have hesitated with sending your listen histories to ListenBrainz in the past, you should now feel free to send your listen information to us!
And it’s been on a steady climb since 
At the time, the website was very limited, with just a page of listens and some very limited statistics. No cover art, no interactions (not even simply loving a track), no listening to music, nothing else than the bare minimum.
We’ve come a long way since and have improved every single aspect, and I think our users were able to see that and recommend it.
In the past couple of years, after a significant redesign in 2023, we’ve made a more significant push to publicise our regular improvements, doing more outreach on social media, fixing a lot of the sticking points and helping less technically-minded users get on board.
We’re seeing the result of that now, and word of mouth is spreading steadily.