It was surprising news: Warren Buffett's Berkshire Hathaway quietly invested in Taiwan Semiconductor (TSMC) last quarter -- a total of $4.1 billion.

The surprise came about thanks to a number of factors -- the large investment, the quietness of the deal, and last but not least, Buffett rarely bets on tech stocks.

Why was this different now?

It is well known that the Oracle of Omaha is a big fan of Apple's shares - it is not for nothing that the group is the largest stock position in Berkshire Hathaway's portfolio.

For Buffett, the purchase of TSMC is of course logical: He believes in the future of Apple stock.

And TSMC is one of the group's most important suppliers.

So if he thinks highly of Apple, then the company's suppliers are equally attractive targets.

But there is also another point: He does not see Apple as a technology company.