When buying a guest post, why does it sometimes get syndicated to more websites?

Sometimes when buying a guest post, a bunch of other websites will copy paste that guest post on them too. I don't know why this is happening. Maybe the owner decided to use it as filler content on other websites that he owns. Maybe others just copied it and simply left the links inside. I don't know.

Does anyone have an idea about why this is happening and whether it's something good due to bringing more links or something bad due to duplicate content?

Are you talking about the article getting essentially stolen and used as "syndicated" content without the backlinks? That is just folks fluffing their sites' content and trying to appear to be syndicators. Very rare to see a guest post of PBN post actually go viral and get picked up in a good way by sites that aren't essentially stealing content. Always pissed me off.

-ThopHayt

This usually happens in press release sites or some news site. Other than that someone is simply stealing the content

But they are leaving the links inside, and those links show up in google search console. This happened to me for both a 25$ guest post and a 100$ one. Some of these sites are of similar quality and have decent metrics, others are low quality or new GBN(guest posting network)/PBN sites. The content I submitted was of higher than average quality for those respective sites. Maybe the owners liked the guest posts and used it on other sites that they had for filler content but left the links inside.

My real problem is whether this is something good due to getting many backlinks or something bad due to duplicate content issues. And is this a rather regular practice? Does this kind of thing happen often when buying guest posts?

I think what's happening here is that those other sites have setup an RSS so that whenever the site which you got a guest post on posts a new article, those other sites automatically show it on their feed as well.

As others have said, it's autoblogs / RSS syndication. I wouldn't worry about it. Google probably puts no value on those links anyways. But if you're feeling wary of them, you can disavow the domains in your Google Search Console.

its usually happen on news sites

Thanks so much guys for the info. Now I'm not that worried anymore : D