Today's stage design wasn't very friendly to a solo attack over the top of the climb, especially with a headwind to the finish. If he did go solo there's a solid chance he'd have been caught anyway.
And especially it being the first stage.
IMO, if I had to bet, he wouldn't have been caught, but it would've been a lot of effort to gain perhaps 18 seconds or so.
Definitely diminishing returns.
Why would you extert yourself three days after of a challenging Monuments Campaign, when the stages which matter for the GC are stage #4 and stage #5 anyway?
He might as well be "washed up" for GTs ( I doubt it, but whatever) and finish 4° at the next TdF, but people reading so much into this stage crack me up.