The 80s weren't a strong period for investment, they were a strong period of deficit defense spending and tax cuts, which were stimulative. When that became unsustainable, the bottom dropped out of the economy. The history of the presidency since Reagan has been continuous giveaways to the wealthy financed by credit taken out by the middle class on phantom assets that vanish into thin air as the president exits. The way the Reagan era was different was that the asset was American world hegemony as a hedge against the eternal threat of Russia (which collapsed partially because it couldn't spend as fast as we could in Afghanistan.)

(Also, according to every graph on the page you linked, the incomes of the top 5% started their climb in 1981, dipped in 1989, recovered to the 1981 trend in 1993, and maintained it steadily until 2001. I don't know how you're reading that differently. After 2001, even the incomes of the top 5% are stagnant, and the important groups become the top 1% and the top 0.1%.)