They lowered the threshold to four years so they could put Thome in in 2016 (still a questionable decision IMO though I get the intangibles). I think the cancellation of Rose in 2017 and the death of Halladay (who also needed the four-year rule) kind of messed up their timeline. As did the pandemic, big-time. Had they been able to have the 40th anniversary that year they could have just done Trillo and left it at that. But once they knew that wasn't going to be until 2022 that opened the door for these guys.
I think they are also waiting for Utley, Rollins and Howard to all be eligible - and HOF-eligible - together so they can decide once and for all how to handle it. The '80s overkill was weird for sure, but it was important to finally do Abreu. Now they should do Rolen before going all-in on the '08 team (besides Charlie and Gillick who are already covered).