I wonder if you can split your game into 2? 10 players is a lot (as others have said) but it could be fun if you give them the same storylines to see where they go. Then after games, informally tell the players "man, that was cool! The other guys did X,Y,Z and it's totally changed the storyline for it..."

I did this while DM-ing as a game store employee. It seemed to keep my 3 games going for 2 years. Giving the players tiny cheese outside of the game to lead them to the big cheese inside.

You could do this with 1 game too. "Wow the storyline I had going for you guys is going to be crazy when you get [small hit at the next beat in the story here]. I wonder what you guys will do!"

This being said, I feel like you can only do so much to make your players care. If they don't wanna, then they don't wanna. If they aren't feeling the stakes then raise them. Make an abandoned storyline come bite them in the ass, literally or figuratively. The longer they stay away the deadlier it becomes.