I sat down at a 5nl table last week and watched a guy donk bet every single street with bottom pair and somehow river a two outer against my top set, I logged off for the night after that. Honestly the swings are wild but the player pool has enough casuals to make it worthwhile if you just stick to solid fundamentals.
That collapse happens a lot when a team sits too deep after getting a lead. Next time maybe cash out early if you feel momentum shifting, saves the heartbreak.