The trade wasn't well-received at first. Hall has an expensive contract, and the Hawks are obviously not looking to win right now. It would have made more sense to see a top contender acquire him at 50%, but the Bruins were also looking to clear some cap space. In the end, everyone in Chicago was happy with the deal.
Over his career, Hall has played with six other 1st overall picks younger than him. He has the experience to help Bedard adjust to the NHL. He notably helped Jack Hughes and Nico Hischier in New Jersey...and look where they are now!