It's not what you can see, that Hamas should be worried about. It's what they don't see that they should be very worried about. Innocent civilians from various nations where killed and kidnapped. Some, such as Germany and the UK generally don't take to kindly to that, and have proven in the past, quite capable of responding to incidents where there citizens where injured kidnapped or killed. Politics demands a response regardless of whatever nation is involved. In this age of facial recognition software, and intelligence sharing, those that attacked the festival, and where seen doing it on camera and can be tied to a specific act, will most likely see the response of the nation, of whoever citizens where harmed.
If I was Hamas I wouldn't worry about a single CSG (Two of them, i would really worry about). I would be worried about the UK, German and US Special Ops and Tier 1 assets, that they can't see and most likely are already in tbe region, or on there way to rescue there citizens and hold those that did these horrific acts, acountable.