You're right that all elections should be scrutinized. Any reasonable doubt should be investigated, even borderline doubts in some cases.
Does that seem like the case here?
People say there was election fraud because Trump said there was election fraud. He provided no evidence or reasonable argument, in fact it looked pretty clear the whole thing was a con that started months before the election.
The Trump campaign was out of money and spent far more than they had to run ads in the final months, and the second the results started coming in they started raising money to "fight fraud". Virtually all that money went to paying campaign debts incurred months prior. None of their lawyers dared even use the word "fraud" in court because they absolutely no evidence to support it.
Literally nobody is afraid of any investigation into this election. There is concern that this investigation serves only to prolong the con as it's being run by partisan people with zero experience auditing elections who have already violated critical election rules. They have gone to great lengths to avoid transparency, banning all press and oversight.
If you want to spend your money investigating this then by all means do so, but do it properly.
Every Republican official involved in running these elections has said there was no reason to believe there was any fraud. Is there any reason to believe they're lying? Interviews with them are painful, they have the integrity to be honest about how they saw the elections but they know doing so puts their political careers in jeopardy.
Election fraud is a game and if you're just having fun playing, fair play, but it's a debate you can't actually win.