Explain Like I'm Five

I think is a bit of a desperate move and change of tactics. They've tried to rally support to be able to conventionally push back Russia on their turf, but that failed for multiple reasons, like the slow drip feeding of gear. Ukraine cannot reach critical masses like that.

I also think it's a matter of a shift in support. The "red line" has been moved over and over again. Remember the raids of the pro Ukraine Russian troops into Russia? Some of them used HMMVs and that got some backlash from the US already. Generally back then the common consensus was to not use any western gear on Russian soil, only on the occupied Ukrainian one. Now we see more and more countries loosening their stance and allow Ukraine to strike Russia within their borders using their weapons.

So now they can do something they couldn't really do before, and they're trying new things to hurt the enemy and potentially get some leverage out of it.