The only question in this trade IMO is whether we overpaid. In terms of long-term plans, it makes a lot of sense.
I think IT had a better offensive season last year and is a great guy, but Irving is more valuable considering the 2 years under contract, younger, healthier, playoff mismatch problems, and better overall upside. So IT + something does make sense.
Crowder, Zizic, BKN is a hell of a "something", but: Crowder had become our 4th or 5th most valuable wing. Zizic is likely a role player. BKN pick is hard to rate, but you could definitely argue it's worth less than Brown or Tatum (known quantities who we rated #3 and #1 in their draft classes).
Ainge wanted to get two young All-Stars locked up and he did it, while keeping his 3 favorite young players (Smart, Brown, Tatum) and conjuring up the LAL pick along the way.
Eyes on the big picture. We're even in great shape cap-wise, compared to any other team with multiple stars under contract.