But at these words of Uncle Vernon’s, Harry’s exhausted brain ground back into action. Why had the dementors come to Little Whinging? How could it be coincidence that they had arrived in the alleyway where Harry was? Had they been sent? Had the Ministry of Magic lost control of the dementors, had they deserted Azkaban and joined Voldemort, as Dumbledore had predicted they would? “These demembers guard some weirdos’ prison?” said Uncle Vernon, lumbering in the wake of Harry’s train of thought.
Does it mean those words of Uncle Vernon was turned into kind of slow-mo way as a result(compared to) of the fast thinking in Harry head?
in the wake of
2.(idiomatic) As a result of
3.In the noticeable disturbance of water behind (a maritime vessel).