Human intelligence develops over a long period; imagine if it all had to be squeezed into 3 - 5 years.
"OTHER MINDS: The Octopus and the Evolution of Intelligent Life" Godfrey-Smith
The last common ancestor between humans and octopus was a flatworm. So their intelligence has evolved comletely separately from ours in a totally different environment. So they are truly an alien intelligence, here on earth.
Coordinating complex movements is another one that appears to drive intelligence.
Vulnerability in a hostile environment. Together with foraging and coordinating complex movement plans, it is hypothesized that predation pressure when combined with the loss of their shell drove cephalopod intelligence. Trading defense for agility and int would also have provided a competitive advantage when competing for prey.