Sounds like you have a bit of a mess. The C terminal is common, that is where you had the blue wire. On the new stat, you put the blue on B, that is a heat pump command looking to send power to a relay. By putting the Blue wire on it, that was a direct short and you blew the fuse. Hopefully you did not other damage. Some thermostats can be programmed to bring fan on when you call for AC, others do not. Some furnaces energize a relay on a call for AC. With out knowing model numbers or wiring drawings, with the thousands of units out there, there is no common answer. So the C terminal is used on some thermostats which require more power to run than others. Some have batteries that power the stat that do not require the C (common). If your stat is programmable, check the manual, set fan to on when a call for AC. Good Luck, with out more info, not much else can be done.