I don't think ALL the tuskens are dead and that the Kintan sand riders are the fall guys. They're bikers. Their thing is riding their speeders and swoops terrorizing moisture farmers and beat up people in bars, not attacking Tuskens.
To me it makes more sense that its the Pykes wanting to take revenge on the Tuskens. Waiting for Boba to pick up the protection money, maybe tracing his trail back to the camp and hit it before he returned.
There were simply not enough bodies on that pile for all of them, and it makes sense that the Pykes took any survivors as prisoners to be sold as slaves to the spice mines. (as "compensation" if nothing else.)
Putting the blame on the Kintan sand riders is just a ruse, and I think Boba is clever enough to see through it. But he is also very aware that he can't take on the Pykes by himself. Saving Fennec might just have been a lucky coincidence, but pardoning the Gamorreans, hiring the Mos Vespas, (i don't care if they have a official name, I call them that and im gonna stick with it) and letting Krrsantian go is just him building up his forces from the ground up. (the wookie will be back and join him -maybe not full life-debt thing, but at least "well, you told me to not work for scugholes, and you seem like a decent chap")
I see a lot of people online being less than charmed with the Mos Vespas, but as a role-player is see them as his level 1-2 hirelings. They're not supposed to be bad-ass at this point. He trained the Tuskens to ride speeders. Under his tutelage he can make these teens level up a bit.
A finale where Boba frees his Tusken "family" with all his recruits makes sense. Maybe the entire crimelord thing is just a charade and he is still a bounty hunter at heart going after criminals, but this time he is taking down an entire syndicate.