The point here isn't whether this guy clean or not. The point is that you can't trust allegations made by Russia. Any allegations made by Russia are what is called "fruit of the poisoned tree".

And just for example, Navalny was put in prison for alleged and proven in a so called "Russian court of law" financial/commercial crimes.

>He was perfectly fine living in Putin's Russia until 2022

That suggests that Russia was for 20+ years fine with whatever financial crimes this guy had been committing as long as he played ball (and like many there continue to commit while staying loyal to the regime), and is really using these crimes to get him now for political motives. (and, yes, looking at current Russian opposition you can find a bunch of guys who is rich and most probably made their money in Russia not in completely legal way, and i honestly don't have respect for them, yet it is clear that the regime is going after them purely for their opposition)

>and prosecutors also found that the privatization in the 90s was illegal

there has been whole wave of such findings recently (and Supreme Court specifically removed statute of limitations here). As result the privatization is usually nullified, the property gets confiscated by the government, and later it ends up in the hands of Putin's friends, family, loyalists. It is a huge redistribution of assets under the guise of "Russian law"