You have a strange idea of what "really bad" reputation means.
That university certainly isn't a peer to Oxbridge, as you note. But like many research universities that aren't in the top handful, a big part of the reason is inconsistency. They have departments with a very high reputation internationally, and they have departments that are decidedly mediocre.
I suspect the reason this school shows up often on HN is because as far as I can tell the (engineering/CS) programs are consistently appreciated by industry. Very few schools have the reputation of producing graduates who fairly reliable do very well in industry, and can hit the ground running. This seems to be one of them.
That university certainly isn't a peer to Oxbridge, as you note. But like many research universities that aren't in the top handful, a big part of the reason is inconsistency. They have departments with a very high reputation internationally, and they have departments that are decidedly mediocre.
I suspect the reason this school shows up often on HN is because as far as I can tell the (engineering/CS) programs are consistently appreciated by industry. Very few schools have the reputation of producing graduates who fairly reliable do very well in industry, and can hit the ground running. This seems to be one of them.