That is a highly debatable point considering NK it had been developing nuclear weapons well before Obama was President and performed it's first ever successful nuclear test in 2006.
Look, I'm not exactly trying to shit on Trump for the NK bullshit, or any other President before him for that matter. This is an incredibly difficult problem with no real good solutions, and the problem has existed for decades. It's not Trump's fault he inherited this problem, nor is it Obama's. I overall despise Trump, but I actually think engaging diplomatically and meeting personally with NK isn't at all a bad idea, considering literally nothing else before that has worked. Why not try it? Unfortunately, these meetings take a lot of time and work to plan for and tweeting about it doesn't exactly get us anywhere with it, and with a barely functioning State department it only makes this whole issue harder. Who knows how this will all turn out in the end, but I do think it is very dumb to lend praise to Trump or anyone else before him for literally accomplishing nothing so far. At least the precedent for trying to meet with NK has been set. Could you imagine Clinton or Obama trying to meet personally with NK? The far-right media would lose their freaking minds. Now if a future Democratic President wants to meet with NK, they literally cannot complain about it.