I can easily offer an explanation that makes perfectly good sense. Since the Russian "threat" has provided NATO its historic mission and impetus for trillions in military spending, its continuation is paramount for those who profit from "threats". Despite the lack of bombastic bravura, Clinton has greatly expanded sales of military arms over his blustery predecessors. His administration has expedited sales to countries with questionable human rights records and opened markets to emerging democracies which can't afford military "modernization" without needless endangerment of their economies.
NATO expansion will cost plenty, not only in terms of real taxpayer expense to our own treasury, but in terms of money from economies far less able to bear the expense and maintain democratic institutions. Our media will do its best to keep these kinds of problems out of sight/out of mind for most voters, blaming problems on other causes. Meanwhile, Clinton and other "new" Democrats will be rewarded by beneficiaries of these misbegotten policies with well stocked campaign warchests. And as notorious big spender Phil Gramm once said: "Ready cash is a politician's best friend".