I honestly think a large part of the problem was the fact that the island I was on was super tiny. But the strangest part was this wasn’t a build up over several days. It happened in less than 24 in game hours.
Basically, my base was above the cave on the island, which was in the middle of the island. The ocean was about equal-distant on the north and south side of the cave. I was about halfway to the ocean on the northside, the mob of monsters was between the ocean and halfway to the cave on the south side.
Day before monster rush, I was hacking trees apart with my bare hands (cause I needed bark and sticks, not logs) down by the ocean at the south end (cause I use the trees at the north end as a maze to hide my base. night fell, I went back towards my base and cut down some excess trees there till it was day. I then went to the cave, and went back and forth a couple of times between my base and the cave during the day (to empty my inventory).
Then night started to fall on one of my trips back to my base, and I noticed a rabbit. So I went after it (south from the cave) and BAM, monster central! They were EVERYWHERE! just swarming the beaches…it was so hectic that many of the hostile monsters weren’t able to beeline for me, because of all the stuff in the way (which is probably the only reason I survived, lol).
But yeah, It was about 24 in game hours between normal amount of monsters and -BAM- TONS of monsters.
I will admit, when it was all cleaned up, I felt pretty BA. It was a lot of fun! hehe