True, but I would say the comparison to Imperial Russia is better and the provisional government is better. Lemme explain. The government we installed in Kabul in 2001 (by the way, while I don't think we have been in too many just wars, I do say that at least until we killed Bin Laden the war in Afghanistan was just) never had any legitimacy. It was really never a surprise that it fell, its national army that we trained was always running into the hills to join the Taliban and other elements in country. Kharzai was given the euphemism, Mayor of Kabul as the government we put in never really had that much power in the countryside. Assad? Well his family had staying power. A half century in power means you have an authoritarian aristocracy but it means you have staying power. Sure sure, Bush, Obama, Trump, and Biden all called it illigitimate and said Assad has to go, but it had staying power. To be sure after about 2014 the Russians and Iranians took over their defense and the Assad government never really got around to resolving the issues impacting its people that started about 2003 when a certain superpower decided Saddam had to go. Let me give you a short timeline of what started the Syrian Civil War:
1. 2003-2006, Iraq war causes lots of people to flee across the border to Syria. Syria, as some may or may not be aware is a desert country. This means that in good times its able to grow enough food to take care of its population. A refugee crisis? Ehhh, that's not gonna help matters
2. 2006-2011. I know, I know, Sukie buy climate change but climate change caused major problems. I'll see if I can find that study IIRC from the UN, but no matter. Syria saw its population increase and it saw its worst drought in decades. As it so happened, at the same time it was going through drought, Russia was too and its crops failed to meet expectation. Russia's government -deciding it didn't want a repeat of the the famines of the late 40s, early 30s, and early 1920s decided that it would keep the grain for its people. At the same time, the US and EU wanted to tighten the screws on Assad and control his oil and so they denied him aid.
3. 2011 the civil war starts. Stagnant economy, stagnant wages, and costs of food soar across Syria. Assad being an authoritarian sends in the army. The conscript army is very tribal and so often the garrisons were called in to shoot their own kin and so they shot their commanders instead and/or their commanders joined the protestors
4. Radical Islamicists who had seized control of much of Iraq, most of whom were former Iraqi Army troops (you know before Bush decided that it would be nice to disband the old Baathist army without pay and make sure they could take their guns with them, if you aren't going to pay someone to at least not shoot you why the fuck would you let them keep their guns?*), decided that they would help out their brothers against that Alawite infidel poured into Syria.
5. Various munition dumps were seized by ISIS. Both sides started using chemical weaponry. Obama decided Assad had to go for humanitarian reasons. I don't blame him for that. However, given how fucking convoluted that civil war was (almost as complex as the Russian civil war which had whites, foreign interventionalists (the browns), the blacks (anarchists), the greens (peasants, mostly from Ukraine) and the reds) we really should have offered mediation and other than making sure humanitarian aid (food and medicines) got in and munition dumps were taken out of action We talked with the Russians and Turks and fucked that country over good and hard. Russia wanted to keep its base on the Med. Go back into the Zone archives and you will see that I predicted Putin would be fine with Assad going so long as he could keep Tartus. Turkey wanted to bitch slap the Kurds, and we wanted the sweet oil deposits. So you got this fucked up situation where Turks were killing kurds, we were arming Kurds, Russians were supporting Assad, the pentagon was funding one group of rebels and the CIA was actually funding a group of rebels that was shooting a group of rebels backed by the pentagon. It was a fucking mess.
6. Putin decided to show his muscle. So did Iran. So did we. Basically we reached understanding (we meaning all the beligerents other than ISIS) that the US would back the Kurds in the oil rich areas of eastern Syria. The Turks and their non Kurd proxies would occupy lands in the north of Syria, the Russians would bomb anti government groups we and Turkey didn't fully support and for the most part we all avoided bombing and killing each other there. There's even pics taken as late as 2023 of US and Russians cooperating in Syria. Yeah it was fucking mess
7. The clusterfuck remained fairly stable until October 7, 2023 when Hamas (likely at the behest of Netenyahu) launched a wave of terrorism that Netenyahu used as an excuse to crush the Palestinians, knock out Lebanon, suckerpunch the Iranians and drive out Assad and so here we are.
So yeah as I said, Assad was -other than in statements of the western press- seen by most of the world and his own people as legitimate. However, I think like Ceausescu before him he wore out his welcome at home and his foreign partners were too busy with their own issues. The fundamental rule, as Nicholas II, Kerenksy, the Republic of Vietnam, Honecker, Kharzai, etc have shown is if your legitimacy is based on foreign aid and not your monopoly on violence you are fucked. Kharzai and his successors were never seen as legitimate. Assad was, the thing to study is why he lost that legitimacy. Crane Brinton's Anatomy of a Revolution could provide some insight to that.