Maybe it's too far away from your memory or you're just not as informed as you may think, but the Rockets avoided a certain team the previous year in the playoffs. They also didn't have a certain league-leading rival to contend with -- someone that had been getting the better of them that year (3-1)
See, without being privy to hindsight, conventional wisdom -- inside and outside of Houston -- was that the team had 2-3 teams really in their way out West. But 2 specifically: one a nightmare matchup, the other an impressive rival on the rise who'd been getting the better of them.
Houston fans were essentially of the same mind as many a Spur or Mav fan in '07 -- they both had a team they were hoping to avoid (Dallas, Golden State). The Rockets, like the Spurs in '07, had the good fortune of seeing their biggest challenge get eliminated in the first round.
So, you see, Blake, last year's result had a good amount of fortune and a different level of compe ion. The Rockets, being cognizant of that and the reality of the current league, felt their team had to make a move to combat two teams they either didn't match-up well with or felt had probably passed them by.
Which brings me to where this all started: Hakeem needed the star talent of Drexler added to his team the next year to go back-to-back. That's my belief, and judging by the actions of the team, it was theirs too.