Why wouldn't a company like Epic, who is the dominant market player by far, put some funding into smaller open source research projects like this? Godot is no threat to them, and quite the contrary brings positive contributions to the whole industry.
Not only is it good PR, but as they say a rising tide lifts all boats.
Steam (the video game marketplace) gets hundreds of releases each day (seriously), and the vast majority of them are bad, and make no money.
I think if you're looking at serious money-making studios that put out good games (whether they are indie or AAA), I bet the engine distribution would look different than your numbers.
But that's my best guess..
Godot is more likely to be used by people whose games wouldn't earn enough to cross the threshold where they would owe money to Epic had they used UnrealEngine, so keeping them away from Unity makes a lot of sense.