We put our faith into systems built by PhDs every day. People don’t have to understand why airplanes stay in the air in order for them to be the only practical means of rapid international transport.
https://www.nationalacademies.org/news/2018/09/securing-the-...
But I can't observe the operation of an electronic voting system. All I can see is the result, and a fraudulent result looks very much like a legitimate result. I'm forced to understand it (which is likely impossible considering the complexity of modern hardware) or to trust people who have incentives to cheat me.
If people just decide not to believe the results of an election, then democracy falls apart.
Undermining trust in the voting system is an old trick. Unless the voting system can show such allegations to be wrong, its results will remain disputed.