They haven't. The procedures in place only work if the folks in charge are honorable and the voters are trustworthy.
What we have, in the modern day, is a deep skepticism of elections outside of the NATO block and a naive presumption of infallibility inside the block (among liberals, mostly assuming their guys win).
In the US, in particular, even liberals are increasingly distrustful of the physical apparatus of vote collection and tabulation. It's been a long time coming (2000 and 2004 being very nakedly and obviously stolen races). But trustworthiness has taken a real nosedive since 2024.
A recent survey conducted by the Center for Transparent and Trusted Elections at UC San Diego found that only 60% of respondents were confident votes in the midterm elections will be counted accurately.