I think it goes a bit beyond that. The way I understand the story, they shut down because it wasn't bringing the traction necessary to raise the next round. The company needed a VC-backed growth trajectory, which apparently was not happening.
We didn't really have many options. We tried to build a business and failed. We could have tried to raise a bridge financing -- but what are we bridging to in that case? A financing (no), an exit (also not an option, as we found)?
Ultimately spinning things down into a skeleton state and doing our best to operate the service for the coming months (heck, maybe years) was the only path forward.
Re: the OP, I think 400k MAUs is actually pretty decent for a mobile app, but maybe I'm mistaken.