Marcelo Claure is coming up on his 1-year anniversary as CEO, and the company has not fundamentally turned around (with some arguing it has gotten worse). Sprint is burning through billions of dollars in cash with no end in sight, has no clear path towards paying off the current $33 billion+ in debt or financing the more debt needed, lags in subscriber numbers, and still suffers from relative network weakness.
That does not mean the stock is a sell, but other shareholders and industry followers have clearly lost patience. I am surprised that Claure has not yet come under strong criticism. Masayoshi Son trumpeted Claure's hiring last year (and paid him a crapload of money), but seems to have since gone silent in praising the young CEO.