The island was not at the Central Plains nor the Clouds Plains but at sea, which made it a perfect target.
The ones ambushing Lu Li and Hu Lang were Recluse Solar Dragon and two other unfamiliar Human Sovereign Realm warriors. Judging by how furious Hu Lang was, Lu Li could tell that those two—were the two Human Sovereign Realm warriors that fled the Serenity Plains.
It would take Recluse Solar Dragon at least half a year to recover after his Soul Pond was hurt by Lu Li. The fact that Recluse Solar Dragon had healed quicker than expected must be because someone gave him some medicines privately.
By the time Lu Li and Hu Lang went to the Central Plains, they heard that the two Human Sovereign Realm warriors of the Serenity Plains had escaped. They were faced with merely two choices. Either they would find some place to lie low and then plan for the future gradually or they would surrender to major families of the Central Plains.