There's no evidence[2] that Russia hacked the DNC. It's "widely suspected" that murdered DNC staffer Seth Rich leaked the emails.[3]

Even if Marla Maples herself provided the returns to the NYT (and the NYT claims they were sent from Trump Tower), I strongly suspect it would've been in that case a violation of their divorce settlement.[4]

[1] Obviously the NYT themselves didn't steal Trump's tax returns, but their source almost certainly did.

[2] That we've seen.

[3] That theory is IMO ridiculous; my point is that it's also evidence-free speculation.

[4] If it were Marla, and it didn't violate the divorce settlement, why the anonymity?