All that mainly because some streaming services are willing to pay a more competitive amount of money for single (albeit national) weekly game broadcasts to sweeten their offering and get more subscribers.
Of course the NFL isn't gonna turn down $1B per year from Amazon for TNF. They get ~$2B from CBS and Fox each for the combined 10 Sunday games, then another couple billion from NBC for one Sunday night game, and another couple billion from ESPN for Monday night.
I think it's unlikely a single broadcaster would spend $12+B/year for exclusive rights to all games.
