Strictly speaking, I wouldn't say Bigfoot or Loch Ness are conspiracies, they are myths, like all monster stories.
Conspiracy theories adhere more to the principle of the original word conspiracy - that is to say they are theories of nefarious undertakings by an individual or group which are illegal or harmful to others/society.
Werewolves, witches, bigfoot, mothman etc are myths, stories about creatures or supernatural occurrences that defy normal explanation.
UFOs are technically both myth and conspiracy because there are stories of alien "monsters" without proof but there is also a level of conspiracy in that the US government hid away knowledge of them for decades before finally declassifying what they knew in recent years.
But back to the topic. You say there's zero evidence in this case - Why would you expect conclusive evidence when the actual investigating hasn't even begun? No, there is not, at this point, conclusive evidence enough to say that there was widespread fraud to swing the election. There is however enough evidence that some shit could have went wrong to merit doing an investigation to see if there is any conclusive evidence to be found. And it will probably all amount to nothing, but at least it would be done.