> because what you describe is not survivorship bias
then you should look up what survivorship bias is. the visible group in this scenario are the individuals who were caught. which says nothing about any conspiracies or even other more competent individuals. the sampling is also poor.
> mail-in voter fraud cannot be detected, then why do people claim that mail-in voter fraud exists
isn't that obvious? if it were easy to counterfeit currency in an undetectable way for a conspiracy while stupid individuals can get caught. would you be asking this question or would you assume the currency is in a bad shape? this example may actually be too on the nose as there is reason to believe exactly this happens with respect to certain state actors while being mitigated by the relative low volume of cash.
> then you should look up what survivorship bias is.
I know what survivorship bias is. The classic example of survivorship bias is analyzing damage patterns of planes returning from war. Clearly, some planes were shot down and did not return: we know that, because we know how many planes we started with. In this case, though, you are asserting that there are uncounted fraudulant voters (presumably Democrat) who were not caught, even though there is no evidence that they exist: in this way the situation is quite different from that of missing planes in war. You ascribe the frauds' invisiblity to a supreme level of sophistification. The problem with that mode of thought is that it allows us to assume anything, including that the sophisticated frauds are actually Republican. So you can't call it survivorship bias until you show that those "invisible frauds" actually exist; you are going backwards by calling it survivorship bias in order to justify your unfounded a priori belief that they do exist.
> if it were easy to counterfeit currency in an undetectable way for a conspiracy while stupid individuals can get caught. would you be asking this question or would you assume the currency is in a bad shape?
This argument makes no sense. (a) If it's easy to commit a crime, then it's not necessary to be sophisticated to accomplsh it. (b) Widespread mail-in voter fraud is not easy to accomplish, unlike your hypothetical "trivial counterfeit" example, despite what Donald Trump tells you. (c) If only Republicans are getting caught doing voter fraud, then by your argument, Democrats are smarter, which is.... accurate. (d) You haven't even posited a posisble mechanism by which millions of fraudulent votes could be achieved. Believing things without evidence is called "faith" and is not the basis on which we develop laws.