Van der Poel should've done more to make sure Evenepoel caught them after the Koppenberg, and Evenepoel shouldn't have pushed on post Kwaremont. I don't think MvdP went all out to keep the gap but half committing was still qorse than not committing, if only ro make sure Evenepoel got back on.
That said, if Evenepoel had got back on, then Pogacar would've just attacked on the Taaienberg. Still, may as well make it harder for him – it was obvious that Pogacar was concerned about Remco, so lean into it. MvdP actually rode the Kwaremont smartly but Pogacar is just a level above.