What do you do about a bad manager?
Work out which kind of bad you are dealing with, because the response to an overwhelmed manager, an incompetent one and a hostile one are completely different — and treating all three the same is why people stay stuck.
The overwhelmed manager — absent, slow to decide, unresponsive, not because they are indifferent but because they are drowning. This is the most common and the most fixable. Make yourself low-cost: bring decisions pre-packaged with a recommendation, use written summaries they can approve quickly, and take work off them where you can. You will gain autonomy as a side effect.
The disorganised or unclear manager — changing priorities, vague expectations. Impose structure from below: confirm agreements in writing, ask "what would you like me to stop doing to fit this in", and keep a visible list of what you are working on.
The micromanager, who is usually anxious rather than controlling. Over-communicate proactively before they ask, propose a check-in cadence that satisfies them, and demonstrate reliability on something small to buy latitude.
The credit-taker. Create a visible record — written updates, shared documents, copying relevant people — and build relationships beyond your manager so your work is known independently.
The hostile or abusive manager. This is categorically different, and the advice above does not apply. Document everything contemporaneously with dates and quotations; keep copies outside work systems; identify whether it engages bullying, harassment or discrimination policies; and use the formal route — grievance, HR, a union — knowing that HR exists to protect the organisation, which is a reason to be precise rather than a reason not to raise it.
What to do in all cases: protect your own record; maintain relationships and a reputation outside your immediate line; and keep your options current.
The uncomfortable truth. A bad manager is the most common reason people leave, and frequently the rational response is to move rather than to fix someone with more power than you. Trying to change a manager who does not want to change costs years.
And check the other possibility honestly: whether the problem is a mismatch of style rather than a bad manager.