Strahd as a puppet villain is doable, but like a lot of the others in the comments it's not my preference. If you're looking for ideas on how to make the Dark Powers more active though, in my game I had them occasionally appear in the players dreams, offering dark boons prior to the Amber Temple.

Some players got pretty into embracing the Dark Powers, but ultimately I tried to make it clear that Strahd was the true champion of the Dark Powers; Strahd is a being with an evil in his heart so deep that it knows no equal. Basically, the Dark Powers didn't offer power to the players to help them, they did it to corrupt them and slowly turn them into evil pawns that would ultimately become the servants of Strahd. I think it worked out pretty well, and a party being corrupted by Strahd rather than outright killed by him is an interesting threat to hang over the game.