Without a moderator it would be a free for all.
True, but this forum had moderators and still failed. The rules were comprehensive and matched the recommendations CoPilot made

when I asked. Interesting that the actual reason for closure was not given, even today. This lack of transparency gives rise to conspiracy theories (although in this case, no one can be bothered)
AI bashing seems to be offered up as a reason, which I find difficult to accept, as it suggests we are incapable of controlling such contributions. This is a defeatist approach I do not think is credible.
So, here is AI's answer:
1. Decline in User Engagement
Forums like Space.com often suffer from dwindling participation as conversations migrate to faster-paced platforms like Reddit, Discord, and even social media. Fewer active contributors can make moderation and hosting feel less worthwhile.
2. Cost vs. Value Equation
Hosting, moderating, and maintaining forums—even modest ones—requires resources. If return on investment (user engagement, traffic, ad revenue) dropped, the parent company might’ve concluded it no longer justified the expense.
3. Shift Toward Centralised Content
There’s a growing trend of moving user discussions into comment sections on articles, centralised “ask an expert” formats, or subscription-based newsletters. Forums offer decentralised, unpredictable dialogue, which can conflict with streamlined content strategies.
4. Moderation Challenges
Science forums attract passionate debates. Balancing free expression with rigorous moderation—especially on sensitive or speculative topics—can become exhausting. If moderation became too burdensome or contentious, that might’ve accelerated the decision.
5. Strategic Repositioning
Future plc may be reshaping Space.com into a more journalistic or commercial destination, focusing on curated news and multimedia rather than open-ended discussion. Forums might’ve been seen as a legacy feature that didn’t align with newer goals.