This is not a "simple" but rather a totally bizarre explanation.
You expect us to believe that Rudy ran out of the house, leaving the bloody shoeprints as they exist from Meredith's bedroom door to the door of the cottage.
Then, he realized his pants were bloody, so he took off his shoes, left them outside (didn't bring them in to clean them? why not?), came back into the cottage barefoot, and went to the bathroom (the one farthest from the door? why?)
Then, he rinsed the blood off his pantlegs (why not just throw the pants away later?), blood ran down his pantlegs and mysteriously got underneath the soles of his feet (laws of physics, anyone? blood will not flow down and then suddenly horizontally to cover the bottom of a foot, certainly not in such thickness and density to form a clear footprint), and then he stepped strategically on the blue bathmat to leave (in your mind) a perfect imprint that could implicate him later.
Hmm. Seems he's solving one so-called "problem" (which doesn't require solution), while creating another worse problem for himself in terms of evidence against himself.
Or do you have someone else in mind for the bloody shoeprint trail that leads out of the cottage? Not a "lone wolf" after all?
Rudy was a pretty dumb murderer, wasn't he? Not only that, he behaved totally inexplicably. Why go back into the house at all?
If he didn't leave the house first, you're expecting us to believe that, after washing blood off his pant legs, for no explicable reason he puts his shoes with blood on the soles back on (why not wash them too, while he's at it?), and then runs out of the house, leaving evidence for all to see and connect him with the murder.
This is the problem the Innocentisti bump up against all the time: They want to selectively look at the evidence, but you can't; it must be taken in its entirety.