You are right that Bitcoin main technology does not need internet. Internet is just fast way for it to communicate. Core of Bitcoin is math problem that can be solved offline. Some projects like Blockstream Satellite are already building way for Bitcoin to work without internet by using satellites to send information. This would be big help in places with bad internet or during outage. However whether this system becomes widely used depends on if governments will allow it. Since independent network could let people get around censorship and government control it could lead to big fight between decentralized technology and power of governments.