Warren Buffett's Berkshire Hathaway (BRK/B) now has Alphabet (GOOGL) as its 10th biggest holding. The firm revealed in a recent filing that it added a $3.4 billion stake in the Mag 7 giant while trimming its Apple (AAPL) stake by over $10 billion. Marley Kayden explains what makes the move so significant as Buffett begins to make his exit as Berkshire's leader.