There were a number of those types of trades pre salary cap era. Which makes sense. A superstar is a superstar at that time, and if you can afford it, it doesn't matter much what they cost.
Well that, and at that time (01-03) I don't think that draft picks were held in that high a regard; the drafts from 1995-2000 (with the exception of 1998) produced lower calibre players than we're used to. 2002 didn't seem all that great either (and it wasn't). Leading into the draft it was Jay Bouwmeester and some guys (Nash was well regarded as well, just not the consensus first overall). Columbus to 1 doesn't happen if there wasn't a side deal in place to ensure Atlanta doesn't take Bouwmeester at 2.
In any event, the conventional wisdom these days is if you want a superstar you have to draft them, because they very rarely become available otherwise. In the previous era, players were far likelier to test free agency, especially since they didn't have the option until their age 31 season. Imagine Connor McDavid being under team control until 2028. Or Bedard bound to Chicago until 2036? It seems that players these days don't ever want to reach that option unless they have a falling out with their team (and force a trade out where they would likely sign a long-term extension).
Anyways, I'm rambling but first round picks generally weren't as valuable back then, unless you had a Thornton or a Lecavalier or a Kovalchuk at the top of the list. There were several reasons for that, not just the cap reasons we have today.