The Tandy Trash80 wasn't in stores for a full six months after the Apple II.
There's a difference between public announcements and going on sale. Both had been in the works for about a year.
The Apple II went on sale in mid June 1977 in the relatively few geek stores of the time, at $1300 for a 4K model without monitor. The TRS-80 went on sale a month and half later in all the Tandy stores for $600.
Price and availability is why the TRS-80 outsold the Apple II by huge margins for years. See previous post for sales numbers.
It took _16_ years for the Apple II/IIe/IIgs/etc to sell the almost six million you mentioned. In the middle of that, the far less expensive Commodore 64 was pumping out two million a year.
The sheer fact is, the Apple II was not a major factor in the home computer revolution for many years. If it had never existed, the revolution would've still come about in the same timeline.
Perhaps it was popular where you lived or something, but it certainly wasn't what first brought the home computer to millions of people.