IIRC tThis happened in India Pakistan during a flood. All the spiders in the area were displaced and they ended up in these trees where they lived together and waited out the flood. Also, the mosquito population in the surrounding area was noticeably low.
if anything i'm glad they're specifically in the trees, and the trees are very obviously occupied. It's the same reason i very much tolerate orbweavers: they will straight up sit in the exact same spot FOREVER provided they consistently get food.
Love my orbweavers! They stay outside, they're chill and not dangerous, their webs are pretty, and they make less food available for Widows. Just have to check that the light shining from your door window didn't bring a feast of night bugs and attract them to spin right where your face will be when you walk out.
Edit to add: if you cone a piece of paper, and scoop the whole web like cotton candy, the spider will cling to it, so then you drop the paper in a convenient bush and leave it there until the spider has had a chance to eat the protein-rich web so it can build a new one.