He allegedly paid for sex work with campaign money, which is why Michael Cohen is in prison right now.
Campaign finance violations (his personal lawyer is currently sitting in jail for an illegal campaign contribution he carried out at the direction of Donald trump). Obstruction of justice is pretty well documented in the mueller report. Those are just the obvious ones
The Mueller report also well documented Trump's complicity with those illegal campaign contributions. That's why he was impeached right after the Mueller report was released.
How is obstruction of justice well documented in the mueller report?
Honestly, there's more ground for obstruction of justice charges against Trudeau for his role in the SNC-Lavalin scandal than anything I've seen for Trump.