Well, naturally every company has talent drain. The rockstars will not work long in one company and jump from one gig to the next. But if you have bad luck and hired some slackers, which will happen with the tightest of hiring schemes, then they will certainly stick around.
Thus over time you still have to re-hire people you really need, but get a bigger and bigger amount of people who are just there for the social benefits.
So what can you do to achieve your ambitious goals? Reduce the workforce and try to find a cutting point where you get rid of mostly parasites while keeping your ambitious work bees around.
Usually at the same time of the cut, some of the work bees also get raises and promotions, because then there's some free budget. So if you are an ambitious work bee, then "cutting staff" is actually also good news.
Finding the right cutting point is really the important point and hardest part. For instance you don't want to lay off people who really are performers but for some reason or another (e.g. they just got a baby) they don't perform right now. So at least in the companies I could look inside until now the cutting point is usually well inside the slackers group, so that the people who would recover and then start performing again have a chance to continue.
In the end, even the most tyranical ass-hole leader wants to have as many people as possible work as hard as possible to achieve his goals for him, in exchange for an amount of money that in most cases is peanuts for him. And not all leaders are even tyranical ass-holes.