I will get to your main question—why there is so much more "biblical studies" scholarship than "quranic studies"—in a moment, but I want to preface this by saying that there has been a massive proliferation of scholarship on the history of Islam and the composition of the Quran and the early sources of Islam, especially in the last 50 years. For example Muhammed and the Believers provides a nice introduction to the history of "Quranic studies" at the beginning of its revisionist argument about the origins of that text. We have recently seen the publication of the Oxford Study Quran along with their Study Bible and Jewish Study Bible to serve as an introduction to the scholarly study of that text.

Furthermore, there has been a "quest for the historical Muhammed." J.A. Watt's Muhammad at Mecca and Muhammad at Medina from the 50s spring to mind as two early exemplars of this scholarly pursuit. But the tradition extends back further, such as Horovitz's The earliest biographies of the Prophet and their authors from 1927. More recently, there has been an edited volume from 1991, The Quest for the Historical Muhammed, but also a more recently published meditation on the problems associated with this, "Writing the biography of the Prophet Muhammad: Problems and Solutions" from History Compass 5 (2007).

As for your question about the Hadith's a quick perusal of the article on the subject from Brill's Encyclopedia of Islam reveals a wealth of books and articles stretching back over 100 years.

Finally, Islamic and Quranic studies has been an area of growth within the academy. More and more scholars are making invaluable contributions to the field.

Now, thereis much more scholarship on the history of Christianity and biblical studies. And there are numerous reasons for that. Biblical studies, like Quranic studies or the study of early Islamic sources, rests on the idea that these texts were written and transmitted by humans and thus they can be better understood in that light. In the early modern period, humanist scholars became obsessed with finding manuscripts of classical sources and began redacting them, finding errors and correcting them based on the comparison of different manuscript traditions. These Christian scholars quickly applied this process to the bible, resulting in the Erasmus Bible and the Luther Bible, which sought identify the most "accurate" editions of the Bible. To return to your question about the way words are used differently in the Quran than in standard, Classical Arabic, Luther spent a great deal of time trying to understand the meaning of Biblical Greek and how it differed from the Classical form of the language. This work could be said to be the beginning of "modern" biblical scholarship, and there is an excellent chapter on this in The Book in the Renaissance. It should be noted that I'm ignoring the history of the study of the Bible in the Middle Ages and late antiquity, which are also fascinating and worthwhile narratives to consider, but the idea that the Bible itself—rather than its contents—was an object worthy of study emerged during this period.

There was not really a corollary in the Islamic world about the Quran and there simply were not enough individuals in Europe with the Arabic "chops" necessary to do this type of work at such an early period.

This more "dispassionate" study of the Bible, and later, Christianity continued through the Enlightenment, when scholars applied empirical methods to the subject. Strauss and the other truly "modern" historians and theologians that emerged from this period in the 19th century carried this forth and the study of the historical Jesus began in this period.

It was not until the high point of European imperialism that university academics began to apply these practices to the history of Islam, but this took time. Whereas Greek, Latin, and, to a certain extent, Hebrew were the marks of an educated European, it took time for people in the academic university world to learn Arabic. Additionally, the manuscript tradition of these early texts were not as well known—and still aren't.

So, to put it simply, biblical studies or the study of the History of Christianity has a significant head start in terms of time and number of people capable of learning the information necessary to produce this scholarship.

Are you discussing English language research or all discussions?

Obviously this is a question that’s not necessarily about history, but more historiographical. I could hazard the guess that really this is sort of a matter of preference and access. First, “mainstream preference” is an issue in many time periods of history. For example, classicists tend to cluster around classical Greece and the Roman Empire. For example, there are numerically far more scholars writing about classical Athens the writings of Plato, Thucydides, etc than most other periods or city states of Greece, with the possible exception of Homer. Or for instance, in Roman history numerically more scholarly research falls in the period of the empire. And, tends to cluster around the big names like Vergil, Ovid, Tacitus, Suetonius, etc.

For both Greece and Rome there are lists of texts and fragments that are largely unstudied or haven’t been reexamined in decades. Every year or few years scholars are moving onto these less traversed texts and publishing commentaries and translations, for example Whiteheads 2016 translation of Philo Mechanicus (I believe) was the first translation and commentary into English of the text. You can broaden this topic of preference in the ancient world further and look at the disparity in numbers of those who specialize in Latin literature compared to the pre-Roman tribes of Gaul, Spain, or Germania. Or, Roman historians compared to Carthaginian historians, or historians of the Greek world compared to those of the various Persian empires.

The reasons for this clustering are numerous, sometimes it’s better sources, more established work to comment upon, etc. There’s also the issue of access, a scholar has to specialize in topics for which there are avenues of funding and employment. Receiving funding for research can be far easier when one can show their work will contribute to a given field and engage in established scholarly debates. And, they must give some weight in choosing their specialization towards employment, less schools have an Islamic studies major than have a history major for example. There’s also the issue of a relatively difficult language modern language to learn to undertake the studies of Islamic texts, not to say its by any means impossible but it is an impediment for those from a Romance language background.

There’s then the issue of access to texts, I’m not well versed in Islamic studies but I wonder if the texts you referenced and others are available in printed editions worldwide or if one would have to travel for access to many of them. You referenced a lack of archaeological data, sometimes countries have restrictive policies on archaeological digs or very weak funding for them. There are certainly archaeologists doing digs in Saudi Arabia, Egypt, Oman, Yemen, etc. These studies unless they happen to be undertaken by Americans are not likely at all to be translated into English. That is essentially the job of the historian, to become translator when they wish to access a source that simply is too low on the priority list of being translated widely, tedious as it may be.

Continuing with the topic of access, one must also realize that much of the work naturally is going to be published in Arabic. There are far more Arabic speaking scholars in the field than there are English, major journals in the field and works in the field will publish primarily in Arabic. If you wish to learn more or study the topic academically learning Arabic would be key imo. Just as the classicist usually needs a grasp of French, German, and sometimes Greek and Spanish to access all of the work on a given topic. The vast majority of work on a given subject will remain only published in its original language a smaller minority of very important work will see multi language publication.

The last point I’ll make relates to access but also to the way the western world views the Middle East sometimes. There will be comparatively smaller numbers in Islamic studies because of the way some western populations view the Middle East as a bit of a dangerous volatile place. There will naturally be those who won’t take up studies of the Persian empire because travel to Iran can be difficult for nationals of certain countries. There will also be women scholars who perhaps won’t take up Islamic studies because of the issue of traveling to Saudi Arabia to see different sites and access texts in libraries or museums there. Outright conflict or tension between nations hinders the ability of certain nationals to enter countries for digs or textual access.

To sum I’d say there are gaps in many time periods and topics of history, where certain texts or nation states are more heavily studied than others. Just as the same sort of question could be leveled by someone living in Serbia as to why there is far less work on the Roman Empire translated into and being done in the Serbian language. You’ve also identified in your post the usage of words, and their etymologies and that takes one further into linguistics a more specialized topic of study. Even for the most heavily studied texts and time periods there are constantly appearing updated commentaries and studies examining the usage of certain words and phrases. This type of work takes a very long time to conduct especially when the texts you’ve referenced are very lengthy. Etymologies of words are also generally highly contested. Ultimately it seems you’ve identified these gaps in knowledge both in English studies and in the broader field as a whole. If attempting to solve some of these questions and publishing work on them is interesting to you my advice is you set out to do so. The field of academia is not overly restrictive oftentimes one can get full funding for their PhD, sometimes involving some degree of teaching during the later years of study. And, working on the masters or doctoral thesis will give you the chance to dive into one of the established debates or publish work on an entirely novel topic.

Piggybacking the question: I have noticed that some professed Muslim Quranic studies scholars sometimes take a theological stance. Take Azyumardi Azra from Indonesia for example. I wonder if this has something to do with the development of Quranic studies as a field, or when the "orientals" try to reclaim the field from the "occidents"?

Apologize if the question is unclear; am a bit lacking in sleep.

Thank you! I was trying to find an academic inquiry into the reliance of hadiths, and was unable to find anything.