Weirdly enough, many unsuccessful companies I know of had management too. Correlation isn't causation, but maybe there's something there.

There are also plenty of successful companies and projects without management too. Basically every 1-to-5ish-man consulting shop has zero managers and some of those do wildly well. Some of the best indie games, produced by teams of 3 or 4, had zero dedicated management. Most open source projects have effectively 0 management.

Valve, famously, kept a flat organizational structure for a long time, and certainly was somewhat successful.