Hate to ask this, but, I've become jaded.

Who is behind this software and what's their motivation for it?

PiHole is very simple in that regard, it was created by some dude to fill a niche and has grown into a reasonably robust community which should be reasonably resilient to outside attacks (someone sneaking in a change which adds a "feature" which exfiltrates and sells my data).

AdGuard also is a very known company with an obvious motive, to sell you their software, but they've been around a long time and are widely used and seem relatively harmless.

I'm sure I'm a cynic at this point, but, I feel like I need to know who these guys are and why they are willing to invest in this.