do the tags on prelude cards count towards Aridors effect?
I suppose they do (they are played after Aridor is revealed).
Yes, that is precisely why you first reveal corporations (in player order) and buy your starting project cards, and then reveal Preludes.
The same is true for other interactions, like Tharsis Republic benefitting from a city placed via Prelude (like Early Settlement).
Have I just been really lucky or has Aridor really good starting conditions with prelude?
I haven't given Aridor much thought, but it's true in principle: Aridor can receive an extra boost from Preludes in that they benefit directly from tags on them. There are other corps which do too (Saturn Systems, Splice, Recyclon come to mind), but not quite as much.
However as Ido said, it's in no way a given that they get that much extra income in the very first generation, and it's just as likely to get as many early tags from project cards. I wouldn't necessarily pick a certain Prelude just to maximize Aridor M€ production, when another Prelude suits my starting hand better.