Electrum servers are full nodes, Electrum wallets download the block headers and verify them. So Electrum wallets also completely trust the miners and whichever server they connect to.
Also Electrum wallets send all their addresses to the server, so an Electrum server can spy on everyone who connects to it.
How so? If the electrum servers are nodes, then the wallet only needs to trust the servers, because the servers are already verifying if the blockchain is good or not.
However trusting the electrum servers is easy, just restart the client a couple of times and you get a new RANDOM server each time. If the TX data is the same every time, then it proves that the blockchain you are on is genuine.