The public interest? It is defined by the regime in power, and they appoint puppets who bow to their slightest whims.
It depends on what the "public interest" means. The public right now is angry about the cost of government, and the use of taxpayer money. Spectrum is a public resource, like mining rights, timber rights, grazing rights, oil drilling rights and all the other resources the government sells to private industry. The FCC sells spectrum space to telecom companies to cover its budget. That's how the Bureau of Land Management works too. This has nothing to do with "the regime in power." This has been governmental policy for over 100 years. Sure, they could just give spectrum space to broadcasters for free, or they could sell the rights to that spectrum to willing payers. It's your money. What would you prefer your government to do?