Because of Trump's history. Trump attempted a self-coup in 2020 by trying to overturn the election. This attempt was foiled because many judges, public officials, etc. resisted it, including many Republicans. Now Trump is back in power, and Democrats are very nervous about anything that looks like "Trump packing the government with loyalists" or "Trump trying to gain more power over public officials", because that would make it easier for Trump to attempt a future self-coup.
In short: Framing this as "cutting waste, fraud, and abuse" is assuming good faith, but given Trump's history, he doesn't deserve a presumption of good faith.
(Secondary to that: There's a difference between "cutting waste, fraud, and abuse" versus "shutting down entire functions of government without a replacement". Look at Musk trying to shut down USAID, for example. If Musk wanted to "cut waste, fraud, and abuse", that would mean "reforming USAID to achieve the same outcomes while spending less money". Instead, Musk is proposing to eliminate USAID entirely. Even if not for the self-coup angle, that's clearly not just "cutting waste, fraud, and abuse". Foreign aid is established by Congress, and only Congress has the constitutional authority to eliminate that aid.)
In short: Framing this as "cutting waste, fraud, and abuse" is assuming good faith, but given Trump's history, he doesn't deserve a presumption of good faith.
(Secondary to that: There's a difference between "cutting waste, fraud, and abuse" versus "shutting down entire functions of government without a replacement". Look at Musk trying to shut down USAID, for example. If Musk wanted to "cut waste, fraud, and abuse", that would mean "reforming USAID to achieve the same outcomes while spending less money". Instead, Musk is proposing to eliminate USAID entirely. Even if not for the self-coup angle, that's clearly not just "cutting waste, fraud, and abuse". Foreign aid is established by Congress, and only Congress has the constitutional authority to eliminate that aid.)