Why did this come out now? Perhaps she leaked what she could through back channels.
Hard to say. Maybe her, maybe people who worked for her at the Dept. of Justice, who knows. You're right the timing, a few weeks after the cabinet shuffle, is a bit suspicious...enough time for the Globe to investigate the story if leaked from someone connected. Either way, it's good it came to light.
If true, this can easily bring down Trudeau, this smells like corruption at the highest levels, especially considering how slimy SNC-Lavalin is and that they are still allowed to bid on gov contracts.