Really, the only reason not to try to fully process the backlog, but to instead let the 'easy' immigrations happen (those money/power-backed, both super-rich persons and staff for the super-rich *cough*Mar-A-Lago*/cough*) the 'easy' refusals happen (actual known criminals) and then just throw back most of the people in the middle (maybe honest, maybe not, but apparently nobody has tried to find out) is if you're afraid that due process and impartial scrutiny will let more rightful immigrants in (whilst also identifying others who shouldn't be.
If you can't stack the review system in your 'denialist' favour quickly enough, just make it so that less people get their fair treatment and pretend they've been denied for good reasons. It looks good for your uncritical (or anticritical) supporters, without even a piece of paper saying "send 90% of them back, regardless". Ditto treat any doubt (unreasonable, as well as reasonable!) about legitimacy, or about legal guardianship, or about intentions upon passing through official channels as "guilty unless proven innocent", while withholding the opportunity to prove as legitimate, honourable or even just desperate to avoid a known bad fate and entitled to the compassion of the state by various national and international laws.
But, hey, sweep them under the carpet and dump that carpet over the neighbour's fence, why don'tya?