On point number one, perhaps they didn't see Remco as plan B because he actually hardly has experience in classics and long distance races. Together with the lack of sprint, they may have concluded that he was too much of a gamble to really use as backup. Anyway, I agree that they didn't "use" him as they should/could have.Their main flaws that could have been avoided are IMHO the following:
• Not saving Remco as your plan B: Everyone already said it. Period. No more explanation needed. How would that scenario have come out, we will never know.
• Like Chris Horner said, they didn't need to blow the race to pieces since they had a big chance for winning the sprint in a reduced field. It had some risk and it would have made for a boring race but they would have had more chance of winning.
As for the second point: before the race, Jan Bakelants said that controlling the race and going for a sprint from a group of 40 or so would be Belgium's safest bet. I think so too, but I assume that they didn't do that because it was a race on home soil. They wanted to show dominance, provide spectacle, and I guess for the riders themselves, it was pretty hard not to get carried away by the crowds. Maybe that's also part of the explanation why Evenepoel went so hard so early. Racing conservatively is hard when everyone is shouting you on and you feel their expectations.