Rotten Tomatoes (the review conglomerator) strives to explain why television animation, the long-time bastard child of TVLand, is so "red HOT right now":
1) Rick and Morty: Up 81 percent in viewership from season 2, season 3’s Rick and Morty finale had 1.5 million viewers between 18-49. Those are Modern Family numbers. ...
2) Bob's Burgers: The Movie is coming in 2020.
3) BoJack Horseman is certified fresh.
4) Big stars* are doing cartoons.
5) DuckTales is as well-reviewed as it is popular. ... (etc.)
Let's boil this down. Television animation is popular for many of the same reasons (some listed above) that theatrical animation is popular. It tells an array of stories, many less stereotypical than your typical live-action fare. And animation isn't limited to young, good-looking (interchangeable) homo sapiens as cast members. It can have starfish, horses, ducks, dogs, and gold fish as lead characters. (Hard for live-action to do THAT.)
In an entertainment universe where "different" is often what it takes to break out of the pack, animation can do "different" a hell of a lot easier than live-action can.
Another reason? Animation skews young, and always has. And Netflix, Amazon, and other content providers elbowing their way into content distribution over the internet are eager to attract young eyeballs. Thus, both cable networks and SVOD platforms want plenty of animation mixed in with other programs.
Lastly, animation is economical. Television cartoon budgets are a fraction of their live-action counterparts, so production companies get far more bang for their buck with a season of half-hour cartoons. Production work gets shipped out to where wages are microscopic or Free Money is handed out, and front-end work (the crucial, story-telling part) gets located in Southern California, where the talent pool is wide and deep.
And that's the way it shakes out, here in the second decade of the 21st century.
Personally, I don't think "big stars" have anything to do with the popularity of animation. 98.7% of the viewing audience doesn't know or care who's a "big star".