IMO intelligence is merely a by product of time, evolution and survival so I don't think it would be that unlikely.
Intelligence (as far as we know) requires a brain, which requires a lot of calories to work correctly. Increasing calorie intake requirements is not something that survival-selecting evolution would select for.
Evolution selects for survival, not intelligence. Sharks and other animals have survived very well for millions of years without ever developing a higher level of intelligence. If anything, intelligence seems like it might be a happy mistake of evolution, and potentially very rare since evolution doesn't select for it explicitly.
So far, we're the only species on Earth to have enough of the right combination to get this far. So maybe it only happens 1 in 1000 worlds with multicellular life.
How many planets does that leave in the Milky Way? That's the sort of calculation SETI does.
I began thinking about it by finding out alligators/crocodiles lived during that time, and they have larger brains. I then wondered why, until I considered the fact that they came from laid eggs, and their 'thing' was the ability to get big when evolution supported it. brains require lots of oxygen and egg shells have limits to how much they can allow through them.
my theory is that they were dumb by design, so that genes could activate and allow them to get really big if it suited them.