The reason I'm asking is because it says very clearly on the card that it's passenger:0. But then it has flying which grants it passenger: 1. I'm confused.

The Passengers: 0 would override the Passengers: 1 granted by flight.

It cannot carry due to the Rule of Zeroes.

Does it though? I don't have it's card and I can only find scans of the front side online so I can't really fact check myself but I think your question warrants further investigation simply because I don't think Thanos Throne can actually say passenger: 0 due to it coming out long before the passenger: x keyphrase was instituted. Further, if it was errata'd to say passenger: 0 there would be some mention of it on the WIN which I also can't find. Right now I'm inclined to believe hcrealms is just wrong and it doesn't have passenger: 0 at all... However, since I don't have access to the full card I'm very amenable to being proven wrong.

The Passengers symbol (stick figure) has been around since Batman set and the debut of vehicles. Don’t underestimate the crowdsourcing powers of our community, or the thoroughness of the volunteers that code, proofread, and edit the units section.

I doubt everything and everyone friendo, try not to take it as a personal attack on our coders. That said I was mistaken about passenger being new. I just remember it being mentioned so much in the rules update that I thought it was new but after re-reading some of the new rules primers a little more critically I see that the only new thing about passenger is that it now applies to non-vehicles too.
So then, knowing that its possible, I concede that it is very probable that Thanos Throne says passenger:0 somewhere other than the front face of the card.

I normally fact check independently but I couldn't find this to save my ass. Thanks for clearing this up. Along with the other posters. Damnit I wanted a flying death chair