Strategically and economically, because Russia needs the Baltic ports. The main theme for the last 200 years of Russian foreign policy has been to secure a non-seasonal access to the ocean it can use on its own terms and that isn't thousands of kilometres away from its industrial centres. The Baltic ports were the closest Russia has ever had to this.
Ideologically, because Russian imperialists consider the Baltics lost provinces of the Russian Empire. Putin is a literal worshipper of Ivan Ilyin. As in, holding services at his grave. He's not reacting, he's trying to re-establish the Russian Empire.
Tactically, because the future of NATO is in question. If Trump wins the elections in November and is inaugurated in January, it is well possible that NATO is non-functional next spring. The US would also have withdrawn any support for Ukraine by that point. What would there be to stop Putin? From launching an invasion that is. Once such an invasion has started, there would be a lot to stop it from succeeding.
Wild statements in my opinion. The port argument makes somehow sense but still they have Kaliningrad, why to open another front provided all goes well there?
For trying to re-establish the Russian Empire I don't agree as Russian Empire was so vast you'd need a few more lifetimes to complete a few more dozens of invasions. I would agree with a different wording though, such as he would love to create a land-bridge with Transnistria. Definitely. Though for the moment, I don't see much evidence that he actually trying to do even that. War of attrition is what he actually does.
As for the third statement about future of NATO that feels beyond crazy to me. I can't see how a single person even being Trump could do such huge damage in such a short period. Not because he wouldn't want but because they wouldn't let him. Kennedy died for less.
If there was no war, maybe. If there wasn't an axis of China -Russia, no BRICS rising, maybe. But under this unfavourable timing no sovereign country, let alone the most powerful, could do such things. Withdraw from Ukraine could be a possibility under Trump though personally I seriously doubt it. Lower the intensity most probably.
In 2017 when there was no war, no axis, no BRICS and even allies were doubting its necessity he didn't dissolve NATO. What makes you think he would do now?
Now let's assume that NATO is weakened, not deliberately by Trump, but weakened. Then you could argue that Russian would be tempted to invade, but Russians are not alone, they exist in a coalition this is how they survived the sanctions war, I don't see how they could justify /legitimise an invasion towards Baltic countries. For Ukraine there was a huge build up; 2008, 2014, Donbas war, Minsk 2, etc.
I don't rule it out completely, but let's say that the world would be totally fucked up if Putin decided to proceed with such things. So a bit of long shot for now.
And lastly even if US /NATO completely pulls out, still there are Germany, France, Poland etc., they won't stay idle to watch Russia invade an ally and EU fellow state.
The Russian economy is completely in shambles and requires the war machine right now, otherwise it will collapse completely. Putin is in the unfortunate position (understatement of the year lol) where he needs to start another offensive to keep the war machine going.
Interesting thought. I can't say for sure if it's correct or not, yet kind of believable. Not for invading Baltic countries, I explained why not but to keep the war in Ukraine going, could be the case.