Alright chief (edit: I've been working on this for over an hour now and I have no idea why I call you chief here now that I'm re-reading it) before we go any further we have to dispel one thing right away:

I recognize that the terror basically killed everyone on the left,

I realize you are likely speaking hyperbolically, but I want to make positively sure we're all on the same page here: this is not true. When we hear about executions during the Terror we hear about the big names: Hébert, Danton, Desmoulins... but the reality is while the death toll was high, and any death toll is nothing to be flippant about, it was still a lot smaller than I think most people imagine.

Now as you can imagine, Historians differ on the actual statistics (and so I'm going to directly cite here), but as far as total official executions from 1789 through July 1794 the number is put at about 17,000 across France.^(1) This includes all of those guillotined after being processed through the Revolutionary Tribunals across France. (note: this does not include deaths from the civil war in the Vendée, which had a horrific loss of life). Now you might have seen the number 40,000 floating around. In fact in my favorite overview of the French Revolution, Liberty or Death, Peter McPhee gives this 40,000 number as the likely amount executed after trial.^(2) Tackett also mentions the 40,000 number, but his claim is that this number was the amount who likely died in prisons due to ill health and/or mistreatment, and for deaths that happened before/without a trial. A last interesting note I just found trying to track this down more: McPhee cites a book, Michel Biard's la liberté ou la mort, that Tackett reviewed for journals. You'd think if they'd both read this source they'd agree on the number, but this just means that I'm now extremely interested to read this book and am ordering a copy right away!

Okay back to the show: During the Terror there were about 1,600 executions in Paris (from March 1793 - July 1794).^(3) Paris had an estimated population of between 500,000 and as much as 640,504 during this time.^(4) As I said, while we certainly shouldn't be careless about deaths, that count is probably a lot lower than many people imagine it would be. I just wanted to point this out so that you can contextualize that the sans-culotte are still very much around. Their leadership, first in Danton and Marat and then in Hébert had been guillotined, but the sans-culotte as a group were still kickin.

Ah and really quick, with regards to:

and I assume many of the patriotic sans cullottes joined the republican forces so that depleted their power in some way

yes many did join the army, a few thousand also joined the Revolutionary Army that was conceded by the Convention after the insurrection of September 5, 1793 to go around France and make sure no one was hoarding food and that it was moving to where it was needed. So you do have a point-- though as you're getting at it's not as if all or even a majority of the sans-culotte were out of Paris.

Okay now onto your question, which first off is an incredibly astute question so bravo. We tend to hear of the sans-culotte as some enraged demanding body of angry street folk, but rarely do I think they're humanized in a way where we ask: What did they really want? Why did they want it? Why were they so willing to risk their lives in insurrections? Your question is great: We know that the sans-culotte above all wanted the necessities of life. So who gave them that? Let's track this over the course of the Revolution!

One caveat: the weather was a fickle mistress during these years. Europe was going through the last period of the so-called 'little ice age', which wreaked havoc on the French agricultural economy.

One of the best ways to track how the sans-culotte were doing is through insurrections. When they felt that they were in need, there were insurrections. When they were content, there were failed insurrections, as demagogues failed to get them agitated enough to act. So let's follow the path of insurrections from 1789 through the Directory!

Let's start in the pre-revolution just to set the stage a bit. Now there was a concept in France that the king was the father protector of the people, and that he had a duty to his subjects, and his children, to provide for them in times of need. This was especially important during episodes like the Flour War, when Louis's ministers attempted to bring France's agricultural economy into the modern era and adopt a lassiez-faire attitude, where prices would be set by supply and demand. Unfortunately for starving peasants, watching the price of bread sky rocket, or watching your freshly harvested wheat leaving in wagons because the city 15 miles up the road has outbid your own, just doesn't sit right. The peasants revolted against what they saw (rightly so) as a gross injustice, and the whole project was dropped. During the Flour War the starving peasants appealed to the king as their father, who was being duped by nefarious ministers and couldn't see that they were suffering.

In the run up to the Estates General there was one of the coldest winters on record (1788-1789) and then to make matter worse, as the crops were ripening that summer a hail storm wiped many of the out entirely in the North. Now this isn't the fault of the governments, but it didn't line up well with the attitudes of the newly constituted National Assembly. These men believed in opening up the free market to enliven the French economy. France was a rabbit's warren of customs barriers, with different internal tolls taken moving goods from one province to another. It was a drain on the economy, and the men comprising the National Assembly saw an opportunity to unfetter the French from this languid system. However as had happened during the Flour War, the initial see-saw as prices rose infuriated the sans-culotte, who didn't care about high-minded economic principles, but cared deeply about the fact that a massive percentage of their wages were going towards their food. Combined with the lousy harvests, this meant that often housewives would wait in line for bread starting at dawn, only to be told that they were out. This fury peaked on October 5, 1789, when the fed up wives and mothers of Paris decided that they had had enough of waiting for food that they could barely afford, only to be told there was none. Marching to Versailles, they decided that the problem was the King (their father-protector remember) couldn't see what was happening because he was closeted away in Versailles, the people hidden from his view by corrupt ministers and scheming aristocrats. The aftermath of their march was that the King was forced to abandon Versailles and relocated to the Tuileries in Paris.

From 1790-1792 there were various political upheavals (primarily the King's attempted flight from the country), and there were several disturbances around this, culminating in the Insurrection of 10 August 1792 and the September Massacres. At this point, France had declared War on Austria and Prussia, making the food situation in the cities much more dire, as they now had to undertake provisioning an army. Into 1793 the sans-culotte presented petitions and had demonstrations calling for a maximum price to be set on bread. The Girondins, in power from 1792- May 1793, were adamant supporters of the free market, and steadfastly refused to set a price maximum. As the situation became more dire, the sans-culotte once more rose up in the Insurrection of May 31 - June 2, to oust the Girondins from power in favor of the Montagnard, who were much more amenable to their demands.