Look up the Skripal poisoning. Russian agents have operated in NATO countries before to do stuff like this.

That said, the “hack” theory is pretty weak, I believe it mainly relies on a coincidence that Burisma was hacked last year https://www.nytimes.com/2020/01/13/us/politics/russian-hacke...

However, the computer shop guy claims the laptop was dropped off in early 2019 and this article says the Russians hacked Burisma in November 2019. The email PDFs themselves provided by the NY Post are dated September 2019, so stuff doesn’t add up here.