It was never publicly announced or anything, but the whispers going around the WACA members (which, back in the 1980s and 90s was a pretty reliable bush telegraph) it was a directive from the WACA board to the groundsmen, as an attempt to head off a push by the TV people to move at least some of the Perth tests to Bellerive.
The broadcasters made little secret of their hatred for the timezone issues of holding international cricket in Perth, and they were pushing to get Bellerive into the regular rotation. Keep in mind that this was when the norm was to hold just five tests per summer, so adding matches to Bellerive meant that someone would lose out. That someone was going to be Perth- at the very least in alternating years.
At one stage, it was even suggested that the commentators were under strict instructions to talk up Bellerive as a venue as much as possible. I have no idea if this is true or not, but at the time Richie and the boys did seem to fawn over Bellerive quite a bit.
As a part of this campaign, the broadcasters started making noises about the number of Perth tests finishing in three or four day, and the hit that they were taking in ad revenue. This started to gain a bit of traction within the ACB, and the WACA completely freaked out at the thought of losing their tests.
The WACA honchos, being lovably simple folk, looked across the Nullabor at Burdett's Adelaide and told the WACA groundsmen to get to work.
Now that they messed up the best and most marketable thing about the WACA, and now they're moving heaven and earth (lots of earth, from just south of Collie) to get it back.