[w1zard0f0z]

The dust gets blown off the comet by the Sun evaporating ice particles where it was trapped on the comet. I imagine much of these dust particles would have negative velocities relative to the Sun. So it would take some time for them to start "falling" towards the Sun. In the case of the Lyrids, the Thatcher comet creating this dust layer returns every 417 years so the "dust cloud" gets renewed. Also, the trajectory of the particles that stay in the region where Earth orbits is alerted by the passage of the planets and their gravity pull. As a consequence there are "outbursts" of meteor showers every 60 years - as the dust clumps up to become denser. That's a layman's 2 cents opinion :)

https://en.m.wikipedia.org/wiki/Comet_dust

https://earthsky.org/astronomy-essentials/everything-you-nee...