It was because he was at Alabama. If he had been anywhere else they would have been praised for their great hire. And Saban was making ~$3.5 his first year not $4 mil, IIRC. He took a pay cut. Bob Stoops was making $3+ mil and Joe Castiglione was praised for being forward-looking. ND had previously (2005) given Charlie Weis a 10-yr contract for a reported $30-40 mil and was praised by all for being proactive. This was when he was 5-2 halfway through his first season of being HC. Alabama hires Nick Saban and Miles Brand voices his concern, echoing the media's outrage. Saban's change of mind was standard operating procedure but the media piled on like never before or since in the history of sports broadcasting.
This is another reason why Alabama fans should be ever grateful to CNS. He knew that if he had been anywhere else, e.g., Texas, he would have been exalted far above all other coaches in the sport's history but because he was at Alabama his praise is as measured as it can be. Now the term is a "great run", one of the "best runs in college football", etc. When in fact it is easily the greatest run in the sport's history during its most competitive era, in the most competitive conference and the most competitive division in the sport's history, with the highest stakes; it is one of the great runs in American sports, pro or big-time college. "We want Bama" became an American idiom transcending football (there were several nations, including from South America, Europe and Africa who held up such banners during WC and Olympic soccer), as well as NFL and HS football teams. Other sports too, though I have forgotten the details. It meant that you were ready for the big time, either in jest or sincerity.
He changed the sport in the way it was played and even more in the way that it is managed and administered. It is a completely different sport now than it was in 2006 - and that was without the NIL and TP changes. In an article ~2 or 3 years ago, in the off-season, Ryan Day said that every decision they made and everything they did was with Alabama in mind. But few will give him his due because he did it at Alabama. Alabama does not even get credit for the small things like the medical tent, etc. "How can those rubes make any meaningful contribution to anything?" Nick knew this and stayed anyway. (IMO, not the, but a primary reason was Mal Moore, whose spirit CNS deeply appreciated.)
But the bias against Alabama is very real and it is not because of Saban's success, it existed long before, it has only intensified because of his success.