Observed, but not understood

I've been trying to come up with a charitable explanation for the actions of a driver I saw this morning.

I have to drive to work a few times a week, because it's so far out of town. So I was doing that, this morning, on a bright, sunny, 20-degree day. Perfect for biking, and I was clearly not the only person that thought so, because there were a lot of bikes out.

One was on Heron Road heading west. I had two whole lanes to work with, so I moved over into the inside lane to pass him. I admit to sometimes making big, deliberate, obvious, signaled lane changes to give bikes room when I'm in a car, because I feel like I'm setting a precedent for the cars around me. So I did that. And I admit, I watched in the rearview to see what the little white sedan that I'd seen coming up a bit quickly in the outside lane would do.

And so I watched as the little white sedan moved even further right, toward the curb, got in behind the cyclist, slowed down to the speed the bike was going, and continued along behind him. Close(ish) behind, pulled way over.

I swear I saw him flash his headlights (which, if it was intended as a "speed up" signal to the cyclist, is both nonsensical and not very useful, since cyclists often have no way of watching what's happening behind them).

And I couldn't figure out what was going on. Was the car slowing up behind the bike as an exaggerated, "you're holding everyone UP!!!" kind of gesture (in which case, fail)? Or was the driver being some weird form of passive-aggressive? Or did they think if they slowed up behind the bike, they'd force passing traffic to change lanes, and so were, oddly, trying to protect the cyclist? (In which case, thanks, I guess, but you really don't need to mess up the flow of traffic for someone who was doing just fine without you. We're good, really we are.)

I couldn't help watching in my rearview, until it got distracting and I had to stop. It was too weird. Two or three blocks later I had to turn off, so I lost sight of them, but the sedan was still, to the best of my knowledge, crawling along behind the cyclist.

You choose: Misguided aggressive driver? Or misguided considerate driver?