For some more details, you will notice (bankrate.com is a good site to check) that higher rates are usually found among smaller institutions.
This is sometimes referred to as a “small bank premium.” They also will often raise their rates more quickly than a large bank.
A lesser-known bank, especially one with fewer branches, will often need to pay more in order to attract deposits. These are also often captive banks that fund credit card operations (like Discover Bank).