I heard from a friend a while ago that there are scholars who believe that putting people into kollel, or everyone studying torah all day on general, is something new in Judaism, that it stemmed from an "Et Laasot" after WW2 that there were no people left to learn, and the torah was in danger of being forgotten. And preferably, it would be better to take a job and have Torah as a side. What is the source for this? Looking for both rabbinic and scholarly sources.
This can be debated with sources and counter-sources forever and ever, but any reasonable treatment of the subject will involve this passage from the Talmud, Brachot 35b:
ת"ר ואספת דגנך מה ת"ל לפי שנא' (יהושוע א) לא ימוש ספר התורה הזה מפיך יכול דברים ככתבן ת"ל ואספת דגנך הנהג בהן מנהג דרך ארץ דברי ר' ישמעאל ר"ש בן יוחי אומר אפשר אדם חורש בשעת חרישה וזורע בשעת זריעה וקוצר בשעת קצירה ודש בשעת דישה וזורה בשעת הרוח תורה מה תהא עליה אלא בזמן שישראל עושין רצונו של מקום מלאכתן נעשית ע"י אחרים שנא' (ישעיהו סא) ועמדו זרים ורעו צאנכם וגו' ובזמן שאין ישראל עושין רצונו של מקום מלאכתן נעשית ע"י עצמן שנא' (דברים יא) ואספת דגנך ולא עוד אלא שמלאכת אחרים נעשית על ידן שנא' (דברים כח) ועבדת את אויביך וגו' אמר אביי הרבה עשו כרבי ישמעאל ועלתה בידן כר' שמעון בן יוחי ולא עלתה בידן
Our rabbis taught: Deuteronomy says you shall gather your grain. What's the novelty in that?! Because Joshua Ch.1 says this text of the Torah shall never leave your mouth, I might think that was intended literally; therefore the verse taught you shall gather your grain -- treat the words of Torah with worldliness [Rashi: as if you are starving, how will you study?]. These are the teachings of Rabbi Yishmael.
Rabbi Shimon son of Yochai, however, said: Is that possible?! If a man is plowing when it's plowing time, planting when it's planting time, harvesting when it's harvesting time, threshing when it's threshing time, winnowing when it's windy -- what will happen to the Torah that way?! Rather: when the Jewish people follow the will of God, their work shall be done by others, as Isaiah says: foreigners shall stand up and tend your flocks; when the people are not doing the will of God, then they'll have to do their own work, as Deuteronomy says -- you shall gather your grain. Not only that, they'll have to wind up doing others' work too! As Deuteronomy says [if you disobey God, ] you will serve your enemies.
Said Abayei [several generations later]: many followed the teachings of Rabbi Yishmael, and they succeeded. Many followed the teachings of Rabbi Shimon son of Yochai, and they did not succeed.
The plain reading of Abayei's conclusion is that for the "many", at least, Rabbi Yishmael's reading is right: go work.
Why do you think that "everyone" is studying in kolel? Last time I looked, unfortunately the majority of world Jewry doesn't even keep Shabbos. A minority of those who keep Shabbos make sure to learn Torah every day, and a tiny minority of those are learning in kolel. We have far less of the required 1 in 10 or 1 in 12 who should be learning full time. When we get to the point that 1 in 12 male Jews are learning in kolel, it will be a different discussion.
A certain percentage of people studying full time was always considered a necessity to the Jewish people, starting from when we were in Egypt.
(Rambam, Hilchot Avoda Zara, 1:3):
[Jacob] taught others and turned [the hearts] of all those who gathered around him [to God]. He also taught all of his children. He selected Levi and appointed him as the leader. He established him [as the head of] the academy to teach them the way of God and observe the mitzvot of Abraham.
[Jacob] commanded his sons that the leadership should not depart from the descendants of Levi, so that the teachings would not be forgotten. This concept proceeded and gathered strength among the descendants of Jacob and those who collected around them, until there became a nation within the world which knew God.
When the Jews extended their stay in Egypt, however, they learned from the [Egyptians'] deeds and began worshiping the stars as they did, with the exception of the tribe of Levi, who clung to the mitzvot of the patriarchs - the tribe of Levi never served false gods.
They refused to work in Egypt and were saved from being enslaved: (Ramban Genesis 5:4, Shemot Rabba 5).
Later they learned and taught Torah to the Jewish people and therefore did not receive a portion in Eretz Yisrael to farm.
Rambam, Hilchos Shemittah V’Yovel 13:12:
Why did the Tribe of Levi not receive a portion in Eretz Yisrael or a share in the spoils of war along with their brethren? They were chosen to serve Hashem and teach His righteous ways and laws to the masses, as it is written, “They shall teach Your statutes to Yaakov and Your Torah to Yisrael.” For this reason they were distanced from the mundane ways of this world. They do not go out to battle, as do the rest of Bnei Yisrael. They do not claim an inheritance of land, nor merit success by their physical labors. Instead, they are the legion of Hashem, of whom it is written, “May Hashem bless his strength (and accept the work of his hands).” In return, Hashem grants their material needs, as it is written, “I am your portion and your inheritance.”
But, as the Rambam writes next, anyone can choose to put himself in the position of someone from Levi:
Not the Tribe of Levi alone, but each and every person, from wherever he may come, whose spirit inspires him and intellect guides him to stand out before Hashem; to serve Him and know Him, and to walk on the straight path as G‑d has made us to do; and throw off his shoulders the yoke of numerous worldly concerns which mankind seeks out, is thus sanctified to become Holy of Holies. Hashem will be his portion and his inheritance for all eternity, granting him in this world his basic needs, just as He granted the Kohanim and Leviim, as David HaMelech said, “Hashem is my portion and my cup. He supports my fortune.