Keep in mind that their ill-gotten gains include votes, and that a criminal's ill-gotten gains of a crime must be disgorged to hold the criminal to account.
It’s a “who watches the watchers” problem. Many countries have tried to impose the legal system on elections and it invariably results in destruction of trust in both elections and the justice system.
Prior to the election, the information was illegally kept secret, so voters couldn't take it into account.
Now, in a new election, if this candidate stops illegally hiding the information, voters will be able to take the information into account.
Aside from that, there's the other matter that must be addressed, that of the criminal prosecution for lawbreaking.
The rules often appear to exist to punish the just and law abiding, while the unscrupulous simply ignore the laws, win their current sportball match, and then rewrite the laws afterward to legitimize whatever the results were. Really common theme with corporate America.
A lot of campaign finance laws are almost flagrantly ignored, or superficially followed, with a light slap and a candy treat afterward. Corporate laws are almost amazing when there's a fine that "actually" matters, and not just a round-off error "cost-of-doing-business." Company makes $10^11 - $10^9 revenue per year, gets a $10^7 - $10^6 fine a decade later? Right, that was like 100th to a 1000th of a single year revenue fine.
But election laws are completely different. Enforcement of election laws inherently allows unelected lawyers and judges to second guess voters. It puts the justice system above the electoral system, which is corrosive to democracy. What are the checks and balances on the people enforcing those elections laws?
Um, legal enforcement of almost any standard allows unelected lawyers and judges to second-guess "the popular will" — for example, in buying goods and services, many people vote with their dollars for the cheapest option as opposed to quality (as airlines have learned). Without enforcement, this "revealed preference" can drive a cost-cutting race to the bottom on the part of producers — adverse impacts on society be damned (e.g., pollution and other negative externalities).
And voters, in particular, can be subject to buyer's remorse: see, e.g., the recent polling about the increase in the number of Brits who voted for Brexit and now regret it. [0]
[0] E.g., https://www.the-independent.com/news/uk/politics/brexit-poll...
https://en.wikipedia.org/wiki/2016_Austrian_presidential_ele...
While I think it would be suboptimal you could imagine "rerun the elections if the winner breaks campaign finance law or gets support from abroad" as an established norm in western democracies, but that's not the world we live in and the EU would not accept these shenanigans from a populist right wing government.