The only insight I have concerns the Layton temple.
A local newspaper article stated that about 10 years ago the church made a contract with a local farmer that in consideration for an undisclosed amount of money up front the farmers would not sell their land to anyone but the church for a five year period.
Once the agreement was about to lapse, the church made another 5 year agreement.
So for about 10 years the church new it wanted the land. If for a stake center or a temple I don't know but eventually it was announced as a temple site.