Those are weak arguments. Author basically says hacker doesn't want to hack country A because then he will run out resources to hack country B. Seriously?

As mentioned in comment, hacking election is very cheap. On back of the envelop, I think $1 million should buy you enough ads to precisely target handful of swing precincts that will give you just 1-2% of the boost needed to put you over the thin win margin. If US elections were won by say, 25% win margins then it would become more expensive because it would be hard to scale. But most elections have less than 5% win margins these days and there are very good predictions available on swing districts. If you have access to voter registration database, you can literally target your ad at individual household level. As shown by last 4 major elections, just even flipping less than ten thousand household can achieve victories.