Well, it's about Peter Thiel, who also founded the Palantir surveillance technology company. As a source for his involvement with Brave, Wikipedia cites this TechCrunch article, which mentions funding from Thiel's "Founders Fund".
I'd rather criticize Brave for other reasons though, like being led by Brendan Eich or supporting crypto.
This article is ahistoric and unnecessarily conspirational.
Signal and its predecessors like TextSecure have been run by different companies/organizations:
Open Whisper Systems received about 3M USD total from the US government via the Open Technology Fund for the purpose of technology development … during 2013 to 2016. Source: archive of the OTF website: https://web.archive.org/web/20221015073552/https://www.opentech.fund/results/supported-projects/open-whisper-systems/
The Signal Foundation (founded 2018) was started by an 105M USD interest free loan from Brian Acton, known for co-founding WhatsApp and selling it to Facebook (now Meta).
So important key insights: