You can’t compare Reddit and Lemmy. They are different with a different model. Lemmy rely on donation. Reddit has ads and investors.
The dev of Sync did money with Reddit but Reddit had a source of revenue.
Lemmy relying on donation doesn’t have this source of revenue. This is why splitting the revenue of Sync between Lemmy’s devs, instances and Sync’s dev is fair.
If someone donate to the Lemmy’s devs and/or instances, this person allows the sync’s dev to make money on this donation. This isn’t fair.
The sync model with Lemmy is predatory at best and parasitic at least.