Egypt under Muhammad Ali became independent from the Ottoman Empire and started demanding Ottoman Syria become part of Egypt, which Egypt then achieved through war, plus taking areas deep in Anatolia like Konya and Adana: https://en.wikipedia.org/wiki/Egyptian%E2%80%93Ottoman_War_(1831%E2%80%9333)
Egypt even wanted to take over Constantinople.
A few years later the Ottomans went to war again to reclaim land lost to Egypt, but lost and left themselves on the verge of collapsing: https://en.wikipedia.org/wiki/Egyptian%E2%80%93Ottoman_War_(1839%E2%80%9341)
The internet briefly mentions the west didn't want the collapse of the Ottoman Empire to leave a power vacuum for Russia to fill, so therefore supported the Ottomans from being taken over by Egypt. But at the same time, it also says the Ottomans signed a military pact with Russia to help one another in war, and that Russia was arming the Ottomans to defend themselves from Egypt.
This took place roughly at the time when Greeks were achieving independence from the Ottoman Empire as well.
Just generally speaking, what exactly happened? Shouldn't the west and Russia have preferred for the Ottomans to have collapsed rather than survive, given they were enemies? Why did western powers and Russia all support the Ottomans against Egypt, and get Egypt to leave Syria?
Because of the straits. Both the United Kingdom and Russia preferred a weak Ottoman Empire over a potentially vigorous Egyptian Empire controlling the Bosporus and the Dardanelles. They both hoped they can influence the weak O. E. in order to keep the other one shut out. The Russian desires about controlling the straits originated with Peter I, while London became interested to lock the Russian navy and commercial fleet to the Black Sea after the Napoleonic Wars when the Russian military proved to be superb and therefore it allowed the Tzar dominate Europe by diplomatic means and military presence as well. This two leading powers of Europe began a match over the dominance. Part of that was the question of Russia getting somehow over the straits.
The Greek Independence War saw a big Russian effort to crush the Ottoman Empire in 1828. The Russian army was only held up by the British threats about sending the fleet into the straits (and additionally Austrian threats about mobilizing the military against Russia). Otherwise they could have conquered Istambul. Despite the remarkable military success the Russian army had to be withdrawn from the Balkan-peninsula, because London threatened going to war against Russia. The Tzar was forced to sign the Treaty of Hünkâr İskelesi (Unkiar Skelessi), which recognized the Sultan's authority over the straits. Basically sultan Mahmoud II decided who could pass the straits in peace and he could close it completely off when he had a war. Considering the enmity between the Ottoman and the Russian Empire this treaty guaranteed that the Russian Fleet would be closed off from entering the Mediterranean See. That was a great British success.
So the Tzar concluded that in order to conquer the straits he has to fight a war against Turkey and the UK and did not really like the idea. When Muhammad Ali gained more and more power over the Ottoman Empire and seemed to know what he wanted, both the UK and Russia got nervous. They realized that their influence would be over if Ali could have had his way, overthrow the Sultan and build a Cairo based moslim empire which has the straits in its grip and modernize the Middle East just like Ali did it first in Egypt. So first the British gave support to the Sultan and became very frustrated when the Tzar responded with offering protection to the whole Ottoman Empire with the Russian military setting up HQ in the vicinity of Istambul. Pro forma that was against Muhammad Ali, but the real Russian goal was to control the straits which meant controlling Istambul and if it means controlling the whole Ottoman Empire, even better. It took a whole lot of plotting for Palmerston to get the Sultan to renounce this protection and send home the Russian officers.