Elon Musk "secretly" disrupted a Ukrainian sneak attack on a Russian naval fleet by turning off Starlink's satellite network near the Crimean coast last year.
wireless communications can be and are disrupted in several different ways in a warzone. Targeting cell towers, active jamming, interception of messages are all huge concerns and all are solved with Starlink
wired communications are useless on frontlines for (I hope) obvious reasons
Quite a lot of the fighting happens in relatively sparsely populated countryside
And even if we assume cell range is everywhere on land... there's none at sea.
All of it and more is solved by Starlink. While Russians learned how to interfere with it eventually, for some time it was near-invincible comms and still brings huge value.
Buuut... In the end Musk gave UA such a wide access to Starlink because the US and UA authorities paid for it a fat coin and most likely followed the payment with an offer he could not refuse. Until China or Russia eventually launch their own internet constellations, the US has a massive edge over literally anyone else and can grant this edge to anyone without it being controversial. Unlike sending military gear which took a while to become reality and was a delicate diplomatic matter, sending a truckload of receivers with access keys taped on them is basic shopping for UA and just a blip in export statistic for the US