I understand the present US administration would want to stop funding this, and that they have the power to do so.
I don't understand how that has led to the sensor network being dismantled. Surely it would have been cheaper to leave it in place and stop maintaining it?
“Have the power”
They have power, but it’s not actually legal. Congress has mandated funds for this array, the administration wants to cripple it beyond repair before any legal action can catch up.
If you destroy the sensor network now, it is that much more expensive for a future administration to rebuild from scratch.
It's not about the cost, it's about ideology. Same reason they've paid nearly $2 billion in taxpayer funds to energy developers to abandon offshore wind farm projects. The point isn't to save money, it's to stop green energy projects, which is an ideological goal. If their decisions don't make sense to you it's because you're not viewing them through their ideological lens.