As a hiring manager I weigh a candidate's public presence at 10~15% of my initial decision, even more if it's exceptionally impressive. And I hear from other hiring managers that they view this similarly.
If you have good academic qualifications and a great record of past work experience ... guess what, there are several other candidates with great academic qualifications and an impressive work experience. Having a strong portfolio of public work can be what distinguishes you and gets you the opportunity to be invited to interview.
One important note: just having publicly available content isn't enough. It also has to be credible and impressive. Original articles that demonstrate deep expertise and are valuable to others. Serious codebase you wrote yourself or made significant contributions to. Real achievements on things like Kaggle competitions. I sometimes see people including a link to a "business card" type website with their photo and links to their social media or a blurb about themselves. That doesn't impress and won't make a difference.