There may not be any crimes, but that's yet to be determined.
Democrat's bigger concern with the Hunter Biden story is with Independents. Polls clearly show that if Independents had known about the story, enough of them wouldn't have voted for Biden that Trump would have actually won. Unfortunately, this story was downplayed/covered-up at the time, and even mentioning it could get you banned on social media platforms. That doesn't look good for Democrats.
As far as crimes are concerned, that's yet to be determined because the story hasn't been fully investigated. I've always stated that let the truth be the truth, and that we should hold accountable everyone of wrongdoing regardless of political party. Hunter may not have done anything (significant) that's wrong, but he likely also would never have been paid for anything without his father being vice-president at the time. Oh, and he also took $4M from a Russian oligarch while his father was accusing Trump of being a Russian agent. Doesn't look good for Democrats.
Again, your issue is with Independents.
The fact that this Kushner story is just coming out now tells me that Democrats think the Hunter Biden Laptop Story is significant enough that some political misdirection is needed.