The Tatum-Fultz trade was a major gamble. The consensus was Fultz was the best player in the draft. Ainge took a lot of heat for that trade.
The Irving trade was a major gamble. The pick Boston traded could have easily been top 3. The risk was Irving could walk at the end of the contract which he did.
If you look at his trade history, he’s gambled quite often. Even the Kevin Garnett trade was a gamble. He didn’t want to come to Boston initially, but Ainge appeased him with the Ray Allen trade