VCs are naturally risk takers, there is a lot of VC money out there seeking novel projects. Maybe if textual can land some companies like Dell/IBM/AMD/Oracle/AWS who want snappier textual frontends for sysadmins rather than slow/clunky web interfaces for sysadmins/app admins to do stuff like board management controllers and textual dashboards for app/status monitoring stuff. Lower bandwidth/more dependable than web interfaces over slow/spotty interconnections with something like mosh. Seems like an option. Projects like this that add color, etc add a 3rd dimension to a 2 dimensional text landscape and I think that counts for a lot.
Large companies tend to prefer support for any major dependencies, so, companies built around an open-source project typically sell support. Customers might also hire them for consulting, custom implementations using the project, etc.
However, it's not a high-value business so it is somewhat surprising VCs are funding this.
Textualize mention they want to make it so that you can deploy the same code base as a TUI and a web app. My guess this will be additional paid functionality that makes a seamless hosting experience.