Charlie Ergen, head of Dish Networks, has stepped down from his CEO role in order to build up the US satellite TV provider’s wireless business. It will be no coincidence that this move comes just weeks after Sprint’s latest attempt to agree a merger with T-Mobile USA fell apart. The failure of those talks opens the way for Dish and Sprint to resurrect their own on-off courtship dance, and agree a spectrum and network hosting deal that could significantly improve the chances of wireless success for both companies. There are many reasons why Dish and Sprint should get closer – though certainly stop short of a full merger, since both bring significant baggage. Dish has an ailing TV business; while…