Science does not require an unbiased sample from a normal distribution to work. Bias is a technical term that the field of statistics is very comfortable working with. Scientists can also often get good results out of biased inputs.

538 has corrections for bias already. They seem to have worked in this instance - I repeat myself but: massive surprise, Biden still president.

To offer a concrete example here, survery respondents are often biased based on who actually sees and fills out a survey. A common technique used to overcome this non-representative sample is called post-stratification. There are, of course, limits to post stratification especially in instances of low sample sizes, but techniques to overcome issues with data are well known.