I'm curious as to why this question was closed. So far as i can see from reading the reasons a post can be closed, there is no validity for shutting someone down for having their project be bad.
I closed the post for a few reasons:
There were at least 3 or 4 interpretations of what the OP was asking for. You saw a motor specification; Olin saw a perpetual motion machine; Jacen saw an inefficient power conversion; and I saw a poorly construed DC to AC converter.
There was an existing close vote on the question.
There were a number of comments requesting clarification on what the OP was trying to do.
That's a textbook example of when a question should be closed as unclear.
In some cases, the community can edit a question to put in "obvious" details and make the question meaningful. In this case, only the OP could provide those details. The risk in leaving the question open while the details are that answers will come in that are invalidated by future edits. That invalidation wastes the time of the answerers.
I just want an explanation why this guys question was closed for just being stupid.
I want to be really clear on this. The post was not closed for just being stupid. The question was closed because it was unclear and needed more detail. For all I know, the OP has a legitimate reason for attempting to convert DC to AC in that manner or whatever it is they are attempting to do.
there is no validity for shutting someone down for having their project be bad.
That's partially correct. This appeared to be a bad project where the problem wasn't clearly explained. That lack of explanation is grounds for closing a question. A bad project could also still be closed for the other reasons as laid out in the help center.
And going so far as to grant the hypothetical "bad project with a very clearly explained problem that can be reasonably answered within the SE Q&A format", then I believe that hypothetical unicorn question ought to be able to remain open.
First off, thanks for asking your question here in meta rather than creating meta comments on the question. Meta is the appropriate place for this sort of discussion.
Second, every SE site has a different culture to it. Some sites are more tolerant of loose questions, others are not. As you noted, it's not a bad thing, it's just a reflection of the community at that point in time. We're all wanting to creating a site with interesting, high quality Q&A.