Brown aside, a city manager is more remote from democratic accountability than a mayor. So transferring power from the former to the latter may be a power grab but it does not imply less democracy, much less autocracy. Having veto power over a city council is pretty well short of autocracy as well. If a city manager is hired and fired by a city council, the manager is insulated from the public by the council. The manager and council can also blame each other for stuff that goes wrong, a further diminution of accountability. A strong mayor can take the credit but also the blame.
Full disclosure: I did a little work for Brown in his primary run against Bill C. He has been, shall we say, inconstant or at least confusing in his convictions. I don't think he is shallow or corrupt. There is always a chance he will come out with something interesting. For a place like Oakland, I speculate, albeit from a distance of 3000 miles, that it couldn't hurt to try something different.
I still think he had one of the best slogans ever.
MBS
"Serve the people,
protect the Earth,
explore the universe."
-- Jerry Brown, 1976