Why would a Toyota automatic transmission fail 80 miles after a transmission flush?

My research (and experience) indicates that on higher mileage (80,000+ miles) Toyota transmissions, if the fluid has not been changed previously, the friction caused by the fine metal particles in old/dirty Transmission Fluid help make the transmission work. As metal parts wear down this extra friction becomes necessary to transfer power. Putting in slick new clean fluid cleans out the particles and causes the transmission to slip soon after. So you may not want to touch higher mileage Toyota transmissions if you don't know the fluid flush history or if it was not routinely flushed.