Let’s play a game.
You and I are competing. Let’s say we play in a community soccer league. Your team is better than mine. You have stronger, more aggressive players and you beat us bad.
Since I can’t improve my team I need to hurt your team. I don’t really want a direct confrontation — I’m not going to send someone with an iron bar to break your players’ knees. Instead, I find a way to hack into your computer. Rather than do something obvious, I make small changes so that your emails to your players don’t to half the team. I send a fake email cancelling the practice field so when your team shows up, someone else is using it. I delete or change email addresses. I delete incoming emails so you players don’t get the information they need.
Your team, actually much stronger than mine, begins underperforming.
In short, rather than confront you directly, I use my access to your information to create chaos for your team. Your team’s performance suffers because your whole team is trying to manage the chaos I’m creating.
If I’m Vladimir Putin, I don’t want a direct confrontation with the US and it’s NATO allies. So I use my resources to do what I can to sow chaos. I see the weak spots in your political systems and I do what I can to exploit them. I don’t need to cripple the US or the UK, I just need them turned inward, focused on their own problems. I need their political systems to be obsessed with resolving our internal chaos. If I’m Vladimir Putin, I actually don’t give a flying fig about Donald Trump except for his innate ability to create chaos; his clear unsuitability for office makes him an idea president not because he does me favors but because he keeps my biggest political opponent off balance and focused on its own problems and not paying me any attention.
With the US and UK (and hence NATO and the EU) off balance, I’m able to have room to pursue my agenda.
Democratic processes are self correcting so ultimately both nations will sort ourselves out. But that doesn’t change the fact that democratic processes are inherently hackable and we must guard the processes carefully.