Complex sentence: Successive presidents declined the use of the house, however, and it was eventually returned to Post's estate, which in 1980 sold it to Donald Trump, who himself later became President-elect of the United States.
Split into simpler sentences: Successive presidents declined the use of the house, however, and it was eventually returned to Post's estate. In 1980, it was sold to its prsent owner, Donald Trump, who himself later became President-elect of the United States.