Complex sentence: Favor from the khan of the Golden Horde allowed Moscow to gain power rapidly at the expense of Tver, and soon the latter did not represent a credible threat to the former, and a new rivalry was formed with the princes of Suzdal-Nizhny Novgorod.
Split into simpler sentences: Favor from the khan of the Golden Horde allowed Moscow to gain power rapidly at the expense of Tver, with Tver eventually losing all influence to Moscow. However, a new rivalry was formed between the princes of Suzdal-Nizhny Novgorod.