Nothing about their internal structure is openly shown. Nobody knows who actually owns the company and who is pulling the strings.
Based on this long thread, Andrey Meshkov /u/ameshkov is 100% owner of the company. I was also skeptical about AdGuard, but after reading that thread I think my confidence was somewhat restored. Another well known Russian software is Kaspersky. They are still based in Moscow so I don’t trust them. They opened some transpareny centers but I still don’t trust them coz they sold out their US customers to some crappy AV vendor called UltraAV. The installation was automatic without user consent. Kaspersky’s AV engine is very good so they should have known better than to install an ineffective AV vendor. If they can sell out their users like that, they can sell them out to anyone.