Why did it took a long time for oxygen levels to become high?

From my limited knowledge, I know Cyanobacteria started producing oxygen around 2.4 billion years ago. Earlier, this oxygen got used up in reacting with iron and methane but when they were done, oxygen started leaking into the atmosphere.

But it was only near the start of Cambrian that oxygen really began to reach double digits. (Please correct me if I am wrong)

So what caused this oxygen to remain low (by modern standards) for so long? And what did it went up at the end?