bunch'u stupid politics, they are a good hechsher!
At inception (back in the early 1980s IINM), they were definitely not considered as such, as it was founded for political reasons and just sought to acquire more and more brands. I hear that it's much better these days, but still isn't considered top tier (maybe for historical and/or political reasons, IDK). Satmar would definitely not come close to it, and I don't think you'll find it in Kfar Chabad either (except as part of ועדת מהדרין תנובה).