This happened for several reasons all at once. I remember it well.
The biggest reason given by CCP back then was to give a boost to miners. Players that actually mine, but as always, they went about it the wrong way.
At the same time, the NS empires saw an opportunity to vastly increase their resources because mining is the easiest thing to multibox, bot, etc. vs combat multiboxing / botting. You don’t need to non-stop mine to build what you want in the current state of it, just activate omega on your toons for 1 month, multibox + macro or bot however many you want, then let them lapse rest of the time. So they made a huge troll / stink about how poor miners are and CCP being gullible as always bought into it hook / line / sinker.
So they nerfed what was referred to as “gun mining”. Now the game is predictably overran with multiboxers / botters and all that sort of crap as a result. Ratting bots are still there of course but not as much as mining.
What they should have done is leave the basic mining alone as it was, but give it serious boosts for active, actual gameplay instead of AFKing and automating, while slightly reducing the reprocessing and reduce loot drops significantly but upped their average quality. That way, people who wanted to AFK mine could still do so but at reduced effectiveness, while those who actively played would get greatly increased results for their effort. This would have reduced multiboxing / botting while at the same time given miners the boost which they needed and somewhat preserve extra income for combat oriented players. Instead they just made blanket nerfs and blanket boosts and then bumped NS ratting rewards to stupid out of whack proportions.
I also would like to see salvaging to be a lot more used all across, so that salvaged components are used in far more construction, especially of the bigger ships and structures, as it tends to be a bit more active gameplay then mining, often done by players right at combat sites or missions after being completed.