The transactions necessary to open and close lightning channels cost sats per byte. When main chain fees are low, it is an opportunity to for lightning node runners to do some cheap housekeeping of their liquidity by opening new channels or closing unprofitable ones.

When on-chain activity is low, some low-rent shitcoin influencers and open-mouth-diseased YouTubers use it as an opportunity to farm engagement by spreading dumb, recycled ideas about how bitcoin is dying.