From the business side you get a notice of the chargeback along with the statement the customer provides when they file it. You then have some period of time, a week or two, to respond. Businesses get scammed by charge-backs too, you know. So you have the opportunity to submit your paperwork showing why you are entitled to the funds. A surprising number of the times the business doesn't even bother.
The credit card company looks at what the customer says and what the business says. They may ask either party for clarification or more documentation. They always prefer the vendor and the customer to settle things themselves so they look to see if the customer reached out to the vendor for some help and resolution first. So if you have a problem you really want to do this first. Documenting emails, phone calls, chat-bot transcripts you, as the customer, have with the vendor is extremely useful here. What's also useful are screen shots of a website that doesn't offer any way to contact the vendor and initiate a refund.
They look to see what the vendor did to try to resolve the issue. Then they may look at the actual evidence. And they may have internal data, like a vendor has a lot of other complaints and charge backs for similar reasons. Or that a customer has a lot of charge backs that weren't upheld.
All things being equal the one with the better documentation generally prevails.
My personal experience is some cards are more likely to stick up for their customers. These tend to be the cards that pay high rewards because the customer pays them directly (the annual fee). Some, like USAA, seem to just be more oriented to helping their customers. But this is totally anecdotal.
One thing I've never heard of is anyone getting 'banned' for making a charge back. If someone has personally experienced this, not just heard it happened, please leave a comment.