I don't think anybody can really say at this point, definitively, who won the trade. I don't think we'll know the real answer to that until the next season at the earliest.
How well Cleveland comes out of it will really be determined but what happens with lebron and Isaiah next season. If Lebron leaves and they choose not to resign Isaiah to a max, then all that really got out of the deal is Crowder, Zizic, Brooklyn 1st. That's a solid return but not a spectacular one by any means.
If LeBron resigns and the Cavs bring Thomas back too, then short term they won the deal. Thomas is really only a small downgrade from Kyrie, so it's almost like they've added Crowder, Zizic and the Brooklyn 1st hurt nothing really. Long term, 3 years from now lebron will be 35, Th Thomas will be 31 and will lose a step, and they'll still be paying Thomas 30m a year... so by that time they might be starting to look like the losers.
For Boston there are just so many variables.
Firstly as good as Kyrie is right now, he's still only 25 years old. Most players don't reach their peak until 27-28 (e.g. Thomas, Crowder, Bradley all had career years around that age) so the scary thing is that Kyrie still has room to grow, and he probably will - especially under Brad Stevens. He's already better overall then Thomas ( who I'm going to guess peaked last season) so the sky really is the limit.
Secondly, Boston has so much young talent. Smart is still only 24 or so, and some he hasn't shown much improvement this far there's still 2-3 years before we can truly write off his upside. Jaylen Brown was already contributing least season as a 20 year old rookie, and he hasn't even began to touch his potential yet. Tatum at 19 hadn't played an nba game yet and is already wowing me with his impressive offensive versatility and amazing footwork - he's almost certainly going to be a stud.
Rozier is has slown serious flashes of potential desire the fact that he's only around 22-23 and had had minimal opportunity. He's a guy who could potentially (given a more steady role) break out in a big way.
Horford is being rediculously overpaid and is way too old to fit in with the rest of this rooster, so ia big part of me hopes he gets traded away for a younger and less costly player who can grow with the team. If not, then he at least offers a steady veteran presence and will have his impact on the game on both ends.
With the exception of Horford, Morris and Baynes we really have no idea what to expect from this team who's only returning starter is Al Horford, and who's longest tenured player is now 24 year old Marcus Smart. This is a whole new team we have right now.