What is the stimulant Captagon? And how did it bring down the Syrian Regime?

how a simple drug could collapse a long standing regime

You've misunderstood something. The Assad regime in Syria produced the majority of the world's black market supply of an almost universally illegal stimulant. The regime fell because proliteriat revolutionaries leveraged sustained physical violence.

Look up the opium wars. Shit’ll blow your mind.

But seriously, I don’t know much about that particular drug. What I do know is that the Assad regime has been largely propped up, for some time, by the aid of Russia and Iran. With the war in Ukraine eating up much of Russia’s stockpiles of funds and munitions, and the war in Gaza and Lebanon drawing Iran’s attention it was an ideal time for the rebels, with the backing of Turkey to strike. To the extent that illicit Captagon sales raised significant funds and arms for the regime fluctuations in demand and regional crackdowns may have exacerbated their weakened position, but the larger effect has to be attributed to the loss of support from international allies.