Since the Sixers want to unload Harris with Simmons, and they won't trade for players like Sabonis or John Collins due to Harris being on their roster, this is the best offer Indiana can do without crippling their roster.
Philly will get out of Harris' absurd deal and have the option to free up 22 million in salary if they let Lamb and Warren walk. The Sixers get salary cap relief.
Sabonis is an all-star who would even be able to hook Embiid up with rest days. I know Sabonis isn't great at stretching the floor, but he's better than Simmons and on a great contract. Sabonis actually shot well in college from 3, so it makes sense he's steadily improving there.
The Sixers get a couple of first round picks since Sabonis is the only high level guy they land. LeVert would be a great 6th man, though. Plus the Sixers land a couple other veteran 3 and D pieces who can help come playoff time.
Indiana just shakes things up. Harris' deal is only 2 more years after this. They would have an interesting starting lineup: Brogdon, Duarte, Simmons, Harris and Turner. Should be enough shooting around Simmons to let him work in space.