The incentives are that Europeans will vote in isolationist parties that are either friendly with Russia, or at best neutral. Those parties will then be anti-EU, anti-NATO. Key word here is isolationist.

Russia knows that if they want to keep annex countries, they'll have to take them piece by piece, with little resistance.

Hybrid warfare. Anything that does damage but does not rise to the level of severity and attribution to be overt war. Russia at a minimum wants Ukraine (and Europe is supporting Ukraine heavily), some analysts think it's not impossible they try a direct attack on Europe in a decade or so, dumb as that sounds.

We've been in an information/intelligence "cold war" for decades and if low-cost, low-risk, high-economic-impact exploits can be exploited, they always will be.

Given the fact that public awareness will quickly push companies to scan all software for vulnerabilities using AI, attackers will be making the most of this period to find daily flaws in hundreds of software packages that we previously saw as either "robust" or "robust enough" given the attack time/cost vs. incentive, before these defensive tools are deployed and operationally effective.

Nation state security services and rogue actors must surely all be scrambling to decide what to do with the millions/billions of dollars worth of exploit development time that forms their tool-set, including potentially using up zero day exploits etc.

The other factor is in the midst of such hysteria as "rouge agents" and other crap piped by the media, along with the actual risks of individuals with a few hours now having as much power as teams with weeks of time to spend did just a few years ago, coherent reports of what's actually going on is drowned in the noise. Attackers take full advantage of this.

Impose costs on a society so that they submit to hostile pressure.

Will it work, or will it harden their resolve to fight?

Hurr durr prices go high, stop paying for arms for Ukraine.

That's always a risk in grey zone warfare, I'd argue it's the 2nd biggest risk after the first which is accidentally going too far.

One being valid does not invalidate the other?

In Russia various security services and oligarchs are always trying to win Putins good will. Which is why they will try various low level sabotage actions like paying some losers on signal to firebomb a warehouse or hack into freezers. Remember there is no possible downside for them.

As a reminder: Russia gave Ukraine tutorial level war from 2014 to 2022, allowing them to fix many problems in armed forces. Resulting in 2022 being far less lopsided than it would be with Russia attempting the same in 2014 or 2015 or 2016 or 2017 or 2018 or 2019 or 2020 or 2021.

Why you would assume that Russian strategy is optimal?

It's not always the Russians, but I don't think OP was saying it definitely was, just that there is a motive.

Noone claimed "Every bad thing that happens is the Russians".

For start several bad things are happening for very clear reasons not involving Russian state at all.

Though "sabotage in Europe has decent chance to be run by Russia" is in my opinion true statement, especially as some cases were linked.

But overdoing "omnipotent Russia is doing everything" in itself may be Russia-run campaign.

Sounds like someone who has never stubbed their toe on a piece of furniture. If you had, you wouldn't forgive those evil Russians so lightly.