Well NK has been pretty consistent here actually. They agreed to the talks mere
hours after the US and South Korea delayed joint military exercises. But then, the
USA conducted additional military exercises in SK anyway, and North Korea
protested about it, but they didn't cancel the actual meeting over it. e.g. this was a point at which NK could have angrily canceled the meeting, but they didn't. And
now, the USA itself basically pulled out over the equivalent of silly Trump tweets from North Korea - one North Korean official said Pence is a dummy basically.
e.g. if you uses some politics-brain, both sides originally
said they want to talk, but NK said they'd only do so if US military exercises in South Korea were halted. When the exercises were halted and NK
immediately agreed to the talks, the USA was honestly surprised. But after that, NK has kept to their word over the talks, while the USA has done multiple things to try and derail the talks - but in a way that they could blame NK for.
e.g. Trump needed to be
seen as the "willing-to-talk" guy and make out Kim as the "non-willing-to-talk" guy. But when the other guy honestly seems like he wants to talk, and you don't, then it becomes difficult to pull out of the meeting in a way you can blame the other guy, so you provoke them by doing the one exact thing they said not to do if you wanted to have the talks go ahead. When that fails, find offense at something silly and tangential. All up, it just looks like Trump was actually committed to either military intervention, or just justifying the continued occupation of South Korea the whole time, and offering "talks" with NK was just the grandstanding part of it that makes out that they're the White Knight in all this.
EDIT: there are also comments from after the canceled talks:
https://www.straitstimes.com/asia/east-asia/china-japan-skorea-urge-continued-dialogue-after-trump-pulls-out-of-us-nkorea-summitOn Thursday, Mr Trump pulled out of what would have been the first-ever meeting between a serving US President and a North Korean leader - a summit with North Korean leader Kim Jong Un set for June 12 in Singapore. Mr Trump said the meeting was inappropriate given the North's "tremendous anger and open hostility".
In response, Pyongyang struck a conciliatory tone on Friday, with North Korean First Vice Foreign Minister Kim Kye Gwan saying in a dispatch via the official KCNA news agency that Pyongyang was willing to sit down with the US "at any time, in any way, to resolve the problems".
There seems to be a definitely discontinuity here between the Trump administration statements and the reality of the situation. e.g. pushing the "tremendous anger and open hostility" point just seems to be a smokescreen to set that up as a media narrative allowing the USA to unilaterally pull out of talks while blaming the other guy. Meanwhile, you have the other guys responding that they're open to
unconditional continuation of the talks, and that's met with literal silence from the US. e.g. it's fairly clearly Trump's side that were looking for an excuse to shut this whole thing down. But, it can't
appear to be Trump who pulled out.