Credibility defined: the quality of being believable or trustworthy
If you examine this definition closely, the word trust is mentioned. The idea here is that if your manager trusts and believes you will accomplish a task, then you have credibility on your side. Without the credibility, you might not even get assigned a specific task or even obtain a job. Credibility must be earned, just as your trust in another person must be earned over time. The more credible you are, the more responsibility that your manager will trust you with. Credentials, such as the very elements you would view on a resume, forecasts credibility but is not the only indicator, which is why you still must prove yourself.
As a brand, you must establish a line of credibility with your peers and co-workers, so that they entrust you with projects and the ideas you conceive. Without this element, you will have no mobility or success in life. Credibility is centric in order to build your brand and push your career further.
Losing credibility is losing trust and losing trust is losing a job.