There is no such thing as 'the mempool'. Every node has it's own mempool with the possibility to set the memory cap size among other parameters. Looking at mempool.space and thelike give you just a sense of what the default node without custom setting might have in his mempool.

For miners there is the incentive to have as much valid tx's at hand. Therefore you can be sure that if just a single miner expects that the mempool might clear one day in the future, there will be a node out there which has set his mempool memory limit to 'almost infinite'. Storage in this memory range is cheap and having 1 sat/vb tx's at hand when the heat clears, means more profit in the form of tx fees mined. As soon as the purge threshold for default nodes drops to 1 sat/vb again, the nodes which have your tx still in their mempool will start to broadcast your tx successfully over the whole network of nodes, mempool.space included.