Legitimacy of the imams

asalamualykum,
I have been trying my best to understand zaydi history, and I come across something that confuses me:

Why is it that bloodshed between claimants of the imammah occurrent? I observe a phenomenon where more than one imam rises to power, and they end up killing each other trying to gain power. Why is it that the opinions of scholars can come to such a sharp disagreement? Why is it that when this issue arises, shura is not what is used to resolve such cases, taking the opinions of all scholars and deciding on what the majority sees fit. Take the case, in 1686 after the death of almuayyad, sahib-almawahib and almutawakkil went to war, and to my understanding they were both eligible for the immamate. My question is, how can two scholars from the prophets bloodline condone such a war that spilled the blood of muslims? wouldn't the natural conclusion be that one resigns from his intent of immamah? Is it not a qualification that they must be well-versed politically to know how to avoid such a war? 

If i may add, i also notice that the condition of having 'the highest virtue' as notable in the book 'The precious necklace', seems to be held more loosely, and power ends up going to the winner of war more than it is about the more religiously pious or the more knowledgeable one, as I could not find a process that pragmatically vets both claimants when they are in dispute.

Wa ʿalaykum as-salām,

Your mistake here is assuming that every claimant to the imamate necessarily fulfills the required conditions. We do not regard every single members of the Ahl al-Bayt (ʿalayhim as-salām) as angels incapable of error. Throughout history, various individuals from among them have claimed the imamate, sometimes in opposition to other claimants, and this occasionally resulted in fitnah and fasād. This does not invalidate the concept of imamate itself, just as the appearance of false prophets does not invalidate true prophethood.

Regarding Ṣāḥib al-Mawāhib, al-Sayyid al-ʿAllāmah Muḥammad ibn ʿAbd al-ʿAẓīm al-Hūthī -may Allah protect him- said in one of his lessons:

“The more his followers increased, the more they wanted to attach new slogans to him. They invented false ḥadīths and composed poems praising Ṣāḥib al-Mawāhib. At that time they exalted him excessively, treating him as sacred, even though they were not qualified for this matter, nor was he deserving of the position of imamate in any sense.”
[END OF QUOTE]

If two true imams, each genuinely fulfilling all the conditions, were ever to meet, one of them would certainly step down out of taqwā. The fact that Ṣāḥib al-Mawāhib did not step down (and is known for a mixture of good and bad deeds) is evidence against him, not in his favor. That does not mean that all of his opponents were legitimate either, for the period was full of turmoil and disorder.

As Muslims, we are obliged to follow the rightful imam. If circumstances make it difficult to determine who the legitimate imam is, we rely on proofs, on the shūrā of our scholars, or we withhold ourselves from the fitnah.

The condition of being “the most virtuous” is a theoretical requirement. Your error is in getting confused on the theory because of historical complications, this would be like doubting Islam itself simply because many Muslims fail to practice it as it should be practiced.

Wa-salām.