He had his pick of the litter this year and chose Buffalo...
It wasn't a bad strategy though - for starters, it appears that Buffalo was offering $3M more than any other team. He knew he'd be playing with Eichel, so it made sense that (theoretically) the two of them would gel together and boost Hall's stats setting him up for a nice long-term contract. Even with the addition of Hall, Buffalo was still considered a long-shot to make the playoffs (nearly everyone had them pegged for 7th in the division) and with a full NTC Hall could decide which team he goes to at the trade deadline - with Buffalo eating 50% of the cap hit and the hit further reduced for the acquiring team since the trade is made at the deadline, this would also theoretically expand the number of teams that could afford Hall versus those that had space this past offseason. By the trade deadline, we could see Hall pick the team(s) that give him the best chance of winning the Cup (which may not have been able to afford him this past offseason) while collecting 60% more salary than he otherwise would've this season.
Things have not been going according to plan so far, given how poorly Hall and the Sabres have been - though if he does get traded and performs well with a new team (particularly in the playoffs), he could chalk the struggles up in Buffalo to being more of a product of the team/coaching.
It would actually be interesting to see a player in the league just take 1-year contracts from season to season. If Hall were to sign with a bottom feeder team with plenty of cap space each of the next few seasons, have a full NTC to dictate where he went at the trade deadline, he c0uld probably earn more money and give himself a good shot of winning the Cup at some point versus signing a long-term contract this offseason.