I think the decision was probably already made before the layoff, barring the postseason miracle that wasn't going to happen then or now.
I'm not sure there is any coach who can get better results with this line-up overall. But a new voice is one of the last cards they have to play. So agreeed, do you want Brand to hire a coach? Do you even trust the guy who hired Brand (and Colangelo) to redirect the franchise yet again? I don't think Budenholzer and Nurse and Spoelstra are better coaches than Brown, I think they work for better organizations.
It would be an interesting year to try and hire a college coach, given there might not be college basketball in normal form and budgets will be cut.
It's hard to believe the Horford move worked out as badly as it did. And that affected Harris too because he's basically fine as an overpaid starter. His salary is more a quirk of the cap system, but if Horford's not your third-best best player and there's no shooter (not even a sixth man) Harris is both of those things, and he falls short there.