The FF resonates and is connected with him. He saw a chance, so he took it. Using a bit of Schala's energy, The Counter-Time Experiment was going to take place in Chronopolis. The moment they started it, Lavos started pulling them back through time, luckily he had ran out of power before he could get them far enough. He may have wanted to get them back to 65,000,000BC when he landed, since he wasn't in a pocket dimension for a brief period then.