This is perhaps the best I have seen so far: CSMonitory - Linking Houthis as Iranian Proxies is a mistake
FTA: "The Yemeni civil war is driven mostly by domestic competition for power and resources in a country that has one of the most heavily-armed citizenries in the world and whose entire post-colonial history has been marked by conflict. The civil war that broke out in 1962 – in which both Egypt and Saudi Arabia were major players – ended in 1967 with the country divided in two."
... There does not exist a natural affinity between the Yemeni Zeidis and the 12er [i.e. follower of the 12th imam] Shia of southern Iraq and Iran. The zaidiya follows a system of religious law (sharia) that more closely resembles that of the Hanafi Sunni "school" of law than that of the Shia of Iran or Iraq. The Zaidi scholars profess no allegiance to the 12er Shia scholarship of the Iranian teachers... In short there is little religious connection with Iran. For a Zaydi to "convert" to 12er Shiism is as big and alienating a step as "conversion" to Sunnism. Such a change would normally lead to family, clan and tribal ostracism.
Sic Semper Tyrannis Col Lang
There are certain peoples who are instinctively good at fighting. The Pushtuns, Somalis, Sikhs and Yemeni Zaidi tribesmen are among them. Others are not so good at fighting or joyful at the prospect of combat; Saudi hirelings of the Al-Saud "country" of Saudi Arabia, Egyptian peasant conscripts, and Sunni Yemenis of the south.
The Zaidi mountain tribesmen defeated the Egyptian Army fifty years ago. There is a large Egyptian military cemetery in San'a. The road down from the mountains to the port of Hodeida is still littered with destroyed Egyptian Army vehicles that were "killed" in guerrilla ambushes.
In the Yemen civil war of the 1960s the Saudi allies of the Yemeni monarchy carefully limited themselves to providing money, materiel and sanctuary in KSA while the Zaidi tribesmen fought a long, long, protracted guerrilla war against the Egyptians and the Sunni Republican Yemenis of the south.
The zaidiya, the form of Islam followed by these tribesmen, is a "legacy religion." It is the oldest and most traditionally minded of the various Shia sects. It is practiced only by the north Yemen mountaineers in their isolated villages and towns high on ridgelines and crests where a dispute often leads to a part of the village moving to another mountain. There are mosques in cities but this is alien ground for the mountaineers.
The zaidiyah is named for Zayd, the fifth Shia Imam. For that reason the Zaidis (or Zeidis) are often referred to as Fivers as opposed to Ismaili Shia Seveners (loyal to the memory of the seventh Imam) or Imami Twelver Shia (loyal to the 12th Imam). These different groups of Shia are NOT interchangeable in their membership and indeed are competitive in their claims as to which was the last worthy imam.
There does not exist a natural affinity between the Yemeni Zeidis and the 12er Shia of southern Iraq and Iran. The zaidiya follows a system of religious law (sharia) that more closely resembles that of the Hanafi Sunni "school" of law than that of the Shia of Iran or Iraq. The Zaidi scholars profess no allegiance to the 12er Shia scholarship of the Iranian teachers. In theology the Zaidis follow the methodology in analysis of the mu'tazila , the "rationalist" school of theology exterminated in the rest of Islam (including Iran) 1200 years ago. This system of scloarship survives only among the Zaydis. In short there is little religious connection with Iran. For a Zaydi to "convert" to 12er Shiism is as big and alienating a step as "conversion" to Sunnism. Such a change would normally lead to family, clan and tribal ostracism."
"This notion is flat-out wrong. Zaydism is related to the dominant Twelver form of Shi‘i Islam institutionalized in Iran in the same way that, say, Greek Orthodoxy is an offshoot of Catholicism -- the statement makes sense, maybe, in schismatic terms, but in terms of doctrine, practice, politics and even religious holidays Zaydism and Twelver Shi‘ism are quite distinct. Moreover, historically, the city of Sanaa and all points north were the Zaydi heartland. Resistance to the Houthi advance did not come from “Sunni tribesmen,” as so many reporters suggest, but from sons of Zaydi tribesmen who, when they joined the neo-conservative Islah, adopted or converted to a “Sunni” identity inspired by Saudi Wahhabism and/or the Egyptian Society of Muslim Brothers. The al-Ahmar clan, paramount sheikhs of the historically Zaydi Hashid tribal confederation clustered between Sa‘ada and Sanaa, and who detest the Houthis, are Zaydi by parentage and Sunni by denominational conversion via partisan affiliation with Islah. On the other side, the majority denomination in the coastal and southern midlands provinces are the Shafi‘is, who are Sunni (in the same way that Lutherans or Methodists are Protestant), but rarely identify themselves as such -- even if historically they distinguished themselves from the Zaydi regimes in Sanaa. Instead, to the limited extent that this conflict is “sectarian,” it is also institutional: It began with a rivalry between Houthi summer camps and the Saudi-financed salafi institute in the small, historically Zaydi town of Dammaj, which is a story rather more precise and interlaced with contemporary state power than the implied frame of “age-old” dispute between the two main branches of Islam allows. 
The second prevalent narrative, advanced from overseas by “brinkologists,” takes the Houthi advance as fresh evidence of Yemen’s imminent collapse. After forecasting state failure for more than a decade, this line of analysis has focused on micro-events, starting with the late October resignation of Prime Minister Muhammad Basindawa’s government and his technocratic successor Khalid Bahhah’s difficulties putting together a viable coalition. The corollary to brinkology is transitology, confidence in international experts’ ability to engineer transitions from authoritarianism to stable liberal democracy (as in Iraq). In this case the transitologists put great stock in, and were hired as expert consultants by, the so-called GCC initiative to stabilize Yemeni politics. The narrative that emerged went something like this: Yemen is on the verge of disintegration, but the GCC monarchies and Western advisers can save it from itself."
Mmh. More later. First time to digest the points. Ruminate and spit out wisdom.