Backtesting bufett fundamental analysis in buying technology companies, and why he is selling part of it

Why did Buffet buy IBM
1) vendor stickiness of services
2) vast global customer base, allowing it to thrive regardless of how technology evolve
3) management ability, divesting low margin business, growing high margin business (consulting , outsourcing)
4) favourable long term prospects at that point of time (outsourcing processes 52%, largest systems and it integration consultant,)
5) management financial management ability, use debt wisely, made value adding acquisition from cash, share buyback
6) technology services companies are less prone to cyclical shocks and growth is more stable , growth industry ,highly dependent on discretionary budget of clients for it services
7) IT outsourcing has Moat like qualities as it is core for technology driven firms (utility) . Switching costs and scale advantages discourage

Why did Buffet sell one third of his stake at IBM 6 years later
1) tough competition
2) new disruptive technology (cloud computing) bring great profits for ibm, but many other business shrinking (X86 server). Lifespan of technology franchise too short. Good call from management shifting resources from businesses in declining markets
3) forex risk overstating profits on the buy years, and eroding profits in the hold years
4) falling short of earnings per share performance targets (continue to decline, prolonged turnabout is hard to forecast )
5) transition to stalwart (rich dividends but declining profit, no certainty of turnabout)
6) deteriorating fundamentals
7) cognitive computing (Watson) created headlines but had not transited to growing revenues
8) Technology has risks of incurring high growth but making no money . Only the last few emerging survivors takes all by establishing network externalities (google facebook twitch Amazon)  while others perish (Bing, yahoo, snapchat, creative, Nokia)

Sources
http://www.businessinsider.com/why-warren-buffett-selling-one-third-ibm-shares-2017-5