I wouldn't call Motorola a failed acquisition - Google bought Motorola as a shield in an increasingly litigious environment: this was the age of Apple going "thermonuclear", Microsoft and patent trolls were wantonly shaking down Android vendors, and beginning to circle Google itself.
Motorola (under Google) had the best value-for-money smartphones - their midrange was solid, and reasonably priced while everyone else was continuously shifting to flagships, with each release priced higher than the last.
From the outside looking in, Google appeared to dispose Motorola to make Samsung happy - Samsung had been complaining loudly and widely about the Motorola acquisition, and openly flirted with other mobile platforms as a hedge.
Motorola shareholders got paid, Google got the patents it wanted, Samsung remained the 600 lb gorilla in Androidland, Lenovo got a good brand and keeps making ok phones to this day. So, not a failed acquisition by any reasonable measure
Google was searching desperately for revenue diversity and was acquiring pretty hard at the time. I think the intent with Moto was to acquire a hardware shop and establish a market leading brand to compete directly with Apple. They eventually arrived at Pixel by building it entirely in-house. That Moto got raided for IP and spun out to Lenovo did not meet those (high) expectations. There was no need for anyone to take a loss but I think Google wanted to make a whole lot of money and did not.
1. It was a crazy time. The winning consortium - which included Apple and Microsoft - invited Google to join their $4.5B bid; which would have made the patents entirely useless as a defense of Google against Apple or Microsoft. Google wisely declined, but bought Motorola less than a year later for $12B. https://www.theguardian.com/technology/2011/jul/02/google-pi...
Source: I was supposed to run the dogfood program in the NYC office. I never got the watches, but somewhere I still have the USB extension cords and the (then quite fancy) chargers with dual USB ports, one for your phone and one for the watch.
And they still do under Lenovo. Multiple-day battery, almost stock Android with very useful enhancements.