Not sure why they were at the front. Both sides been using them as mobile artillery for the past nine months. Just look at the published loss rates and you can see there aren't many on the front line. The Russians occasionally try the whole banzai thing to poke through and lose a bunch, but Ukraine hasn't even done that much since they failed last summer. I'm not sure there's been a single tank on tank (proper MBTs, not misc. armoured vehicles) kill the whole war. Ukrainian tactics are to keep the tanks well back to stop a break if the front retreats. The NATO sort just weep over it, but it's not their war to fight. Ukraine has never really had enough tanks to use them the way doctrine dictates, so they compromise and because of that, tanks just aren't the right tool for them. They'd far rather have more SAMs or artillery. (or better EW, but they ain't getting that)