Mined ore and grain had been being blocked since Russia invaded in 2014....using the Crimean ports Russians have an effective blockade for all shipping in and out of Ukraine. So since they control all shipping out of Ukraine they also get to set the prices they would pay for the Ukranian goods exported...(Which were ridiculously low)
All of this was staged and accepted by the Ukranians last president...when Zelenski came into power....the free ride was now over...so Russia thought that they could invade the entire country and fair, free markets would be over. Things at severely discounted prices could resume.
How many ports does Ukraine control?
Dry bulk cargo in ukrainian ports – PortEconomics
"Ukraine.
"
Ukraine possesses the most powerful sea
port potential among all the countries of the
Black Sea and the
Sea of Azov.
[1] There are 18 seaports located along the Ukrainian coast."
List of ports in Ukraine - Wikipedia
In 2014 a violent coup supported by the US drove a corrupt, yet democratically elected Ukrainian, president from office.
At that time the Ukrainian population was divided over closer ties with the EU and IMF or traditional trade with their closest neighbor.
One side was willing to settle the issue at the ballot box while the other preferred violent revolution that's led directly to the carnage we see today.
Background and elements of the war in Ukraine | MR Online
"Ukraine only an independent country since 1991
"When Putin says Ukraine was artificially created by the Soviet Union, he is correct. Ukraine has only been an independent country since 1991.
"That is only 30 years.
"Previously, it did not exist. Today,
"Poland contemplates recovering a part of it, the same with Bulgaria and, even in Hungary people say parts of Ukraine belong to them.
"The same goes for Romania and Moldova. Moldova itself was a part of Romania. All this is an artificial creation of the Soviets, of Stalin.
"It is a simplification to say that the Russians are against Ukraine. It is much more complex. It is precisely these elements that are not only state-bound, but also cultural."