Open source projects still need a maintainer/owner. For example, Facebook "controls" react, Microsoft "controls" Visual Studio Code, and AdguardTeam "controls" AdGuardHome. There are several reasons to not trust a maintainer (eg, license changes, prioritizing or implementing undesired functionality and anti-features, converting to "open core", abandoning the project, selling out to less trust worthy entities, etc.).
Per Adguard's website, the legal entity behind the various AdGuard products is ADGUARD SOFTWARE LIMITED. A quick search on that company shows that there are 3 founders and they seem to have some ties to Russia. There is more information online about this, but whether this means they can be trusted or not is up to each potential user of one of the AdGuard products.