It's hard to say. I don't think I would've gotten super deep into the dungeons without the help of some cheaters guiding me and dropping duped powerful items, so that was fun. But still, the game had a very compelling single player (which was more important in those days), and I played plenty of multiplayer with people who weren't cheating and it was still fun. So I think it still would've had an impact, especially with the interactive story, the unique controls/method of play, and the good graphics and overall polish (including the prerendered scenes).

PC gaming was very different 20+ years ago. It's not like there was social media chatter about how you had to check out this game with all the cheating and whatnot (maybe people did that on Usenet or something but I wasn't savvy enough to know about Usenet, and I'd argue the majority of new internet users coming online in the mid-late 90s weren't either). There was also no Google, YouTube, etc. to research games to buy - I'd buy a game based off the box art/marketing, or occasionally I'd buy a PC gaming magazine and see what they reviewed. Or talk to my friends and see what they've been playing. I'd also play the hell out of games I bought, partly because I had a longer attention span back then (I think we all did) but also because I'd rarely buy a new game, and we weren't exactly drowning in amazing PC games - there were no Steam backlogs back then calling out to you to pick up a new game the moment you got bored.

In short I don't think people were buying the game based on the cheating aspect. But I do think the cheating gave the multiplayer an unknown quantity that improved replayability and perhaps made it culturally memorable (it seems a lot of people remember the "duping" in here especially). Even so I think there easily would've been a Diablo II even if there was no cheating in Diablo.

I wasn't a Diablo cheater, but I was a Diablo 2 cheater. Frankly, it was what made the game playable for me; I wasn't cheating to dupe items or anything like that, but making the damn map functional. It was definitely a huge part of the staying power of the game, IMO.