It is not Li who is "cowardice", it is the Chinese people in general.
Xi has his advantage over Li: Xi only cares about himself, he would corrupt his followers and colleagues with the price paid by the whole Chinese people, and he did without hesitation and succeeded as others in Chinese history. Meanwhile Chinese people don't know (brainwashed)or don't care(coward as you described).
Leaders who work for his people need these people's support, that is the only source Li could get "power" from and this is the way how a democratic society works--people are willing to participate. Chinese are different, few are willing to participate.
If Li could've seized the power the way Xi did(as many of us may have wished Li to do so), he would've be more like a "Xi" than himself. The two are simply made of different materials. Key is the people.
