The problem with your alleged argument in favor of government land grabbing is that Trump lobbied government officials to act on his behalf. Oh, and guess what? The courts ruled against Trump thanks to Infinite Justice.
Trump may have lobbied the RDA people, but it wouldn't matter. RDA had been condemning property all along ~ usually to assemble lots where there were legal impediments to such assembly by private parties.
We have a 4 acre lot in my neighborhood that has been abandoned for 50 years. The trees are falling down. It was owned by a lady, since deceased, who fell on bad times and ended up in a rest home. Her custodian was unable to negotiate a disposition with the heirs regarding the lot. I think there are now well over 100 people with a property interest in that lot, and most of them are unlocatable.
If we had an RDA it would go to court to condemn the property and reorganize it into something suitible for compatible development.
The heirs would then await their share of the proceeds and we wouldn't have 4 acres of dangerous jungle down the street.
What will ultimately happen absent an RDA is that somebody will get killed by one of the falling trees. Their heirs will sue the pants off the folks who believe they own that lot. That will be a big surprise to them.