While over 2,000 senior NASA employees were reported to be leaving due to budget cuts and pressure during the Trump administration, the claim that Donald Trump 'overnight gutted NASA' by firing more than 2,100 employees including over 1,800 senior employees is an exaggeration and lacks nuance.
Overnight, Donald Trump gutted NASA and America's space flight program, firing more than 2,100 employees, including over 1,800 senior employees.

FactVerify
Source: factverify.com
What the Evidence Shows
The claim states that Donald Trump 'overnight gutted NASA and America's space flight program' by firing more than 2,100 employees, including over 1,800 senior employees. The search results indicate that there were plans and pressures leading to significant staff reductions at NASA during the Trump administration, with reports of over 2,000 senior employees intending to leave or being affected by budget cuts.
However, these departures were not described as immediate firings or an 'overnight' action. Instead, the reductions involved early retirements, buyouts, and deferred resignations as part of a broader cost-cutting initiative. The numbers cited in the sources mention around 2,000 or slightly more senior staff affected but do not confirm the exact figure of 1,800 senior employees fired overnight.
Moreover, the term 'gutted' implies a sudden and comprehensive dismantling of NASA's workforce and programs, which is not fully supported by the sources that describe a planned reduction process rather than an abrupt mass firing. Therefore, while there was a significant impact on NASA's workforce under Trump's administration due to budgetary pressures and restructuring efforts, the claim exaggerates the immediacy and manner of these changes.