You ever wait weeks for a response to an email, then it comes and you respond right away, then they respond right away again? Then you respond right away again, then you respond right away again?
I’m sure you have. Email isn’t a top-to-bottom stack. We respond to emails in a totally random order based on what is loaded into our brains at the moment. Some emails are just hard to answer because they require a bunch of secondary work first. Sometimes you need to brute force them. But once you have, the floodgates open and responding to the next one is easy.