They were likely also hidden behind the SUV that moved over to give them a wide berth. I can actually visualize the exact scenario that happened and be about 100% certain it's exactly what happened, and lights, reflective gear, and helmets wouldn't make a difference in it.
Drunk driver sees two cars going slower (on account of the two on the bikes on the edge of the road). He has a passing zone(or doesn't) and goes to pass said two cars. He gets past the first one, and then other SUV moves over as it's passing the Gaudreau brothers. He gets pissed, and flips back into the right lane thinking the SUV just didn't want him to pass, because the brothers were hidden from view behind the other SUV. If he was passing on a two lane road, where speed limits are generally 55 or 60mph, he was probably doing 70-75, maybe more. As soon as he gets back to the right to try and pass the SUV, the brothers appear into his view from behind the SUV, and are hit.
That's, in my mind, exactly what happened.
He needs to spend a long, long, long time in jail.
I've had situations like this on a road I take to get to my parent's house a lot. It's two lanes, and about 7 miles through the woods. I've gone to pass someone doing 40 in a 55mph zone, in a legal passing zone, only to have them smash the gas pedal to prevent me passing, all the while I now have a car coming at me head-on that I normally would have no problem avoiding had this guy not purposely tried to prevent me from passing, and I'm essentially racing said asshole to avoid a head-on collision. And I had my kids in the car. I did get by him, but it took everything in me not to come to a complete stop in front of him and beat the everliving shit out of him for almost killing me and my kids out of some stupid sense of pride or ego.