What happens if everyone disconnected from the blockchain What would happen if for some reason, every computer connected to the blockchain was disconnected, and no peer-to-peer connection was established with the blockchain protocol between 2 users.
Would all the transactions recorded on the blockchain be lost ?
Also what if theoretically only 1 or 2 connections remained connected to the blockchain, wouldn't it be easy for them to just add more transactions to the chain and everyone would need to trust their blockchain state since there is no other copy of it elsewhere*(or are they stored locally on devices even if they disconnect??)* ?
Computers are not connected to the blockchain.
Computers running Bitcoin software connect to a few other computers that are running Bitcoin software.
Each of these computers keeps its own copy of the blockchain if they are what is known as a full-node. For example any computer running the &quot;Bitcoin core&quot; wallet software is a full node. So even if they don't communicate, this blockchain data is not lost. The old transaction data is still stored on many thousands of computers.

No node ever needs to trust any other. Each node that has a copy of the blockchain can use it to check that new blocks are correct.