The way I understood/understand it is he has continued the sex worker thing throughout their investigation but something more must have triggered this. I think it most likely they were not only surveilling him, probably had him "tapped" in whatever way that is nowadays, they had to be careful who they involved, asked questions of or shared anything with but maybe they were even doing something like placing a tempting sex worker ad they hoped he'd respond to, etc. and all sorts of things. Hard to say... They MAY HAVE even involved the wife as an informant... Probably not but not out of the realm of possibility. Got her alone, told her, told her her hairs were present, etc... and said we don't think you were involved but this is who your husband is and you can cooperate and help or not.. I'm not saying that happened but what I am trying to say is I think somethihg more than him just contacting sex workers triggered this arrest at this time... Some behavior, some plan, some route he took, where he went, something... OR even worse there was another murder or assault they can tie to him but we don't know about yet and they knew they couldn't leave him in public another day or later when the public found out there would be outrage...?