Compared to the websites those phones had to try and consume, there is a lot of HTML!
opera mini does a bunch of magic to strip websites down a lot.
Opera Mini doesn't render HTML, it renders OBML — essentially a binary serialisation of a device-specific render-tree. The HTML->OBML conversion is done in the cloud.
Ha neat i did not know that neat. But i suppose there is still just more OBML to hold in RAM (even if it is more efficient).