1986 Oldsmobile Cutlass Oil in the intake manifold

I have a 1986 Oldsmobile cutlass ciera. I have just replaced to water pump because it was not working correctly. After putting it all back together. I had also changed the fuel filter at the same time. I started the car and it ran for approximatly 5 min then stalled and died. I noticed the water pump was leaking so I guessed that the seal wasnt on correctly. I was going to start all over again and when I took off the tube that runs from the airfilter to the intake manifold it was full of oil. The air filter was dripping with oil and oil came spilling out of the intake manifold. What could have caused this? Is the car ruined?