In my experience, people who are hostile as their default mode, are actually using that hostile persona as a pre-emptive measure - cover for occasions when only hostility can get them out of exchange with others that would otherwise expose them. If they are always surly they can be surly when they need to deflect without being detected. Guilty people have a natural hostile reaction to inquiry ( and that gives away that they are not being forthright and honest BTW).
So dimald uses this surly persona. He also uses his endless lies, often 'silly', in order to evade detection and tracking of the important lies (like lies about conspiring with russia). his endless often silly lies are chaff to cover the malicious and coverup lies. Bad guys use both tactics at once. I'm sure the investigators are experts on this stuff, but I wish the general public had been taught how to recognise cons and crooks. Maybe schools and parents can start teaching their kids how to spot dishonesty and people on take, like trump and many others.