The global reach of Covid and its staying power both as a killer disease and an economic menace attracted a philanthropic response of $20.2 billion last year, more than double the amount given to the previous top 10 disasters combined, according to preliminary estimates released Wednesday. For many nonprofit leaders, however, the true measure of philanthropy’s response to both the pandemic and the racial-justice uprisings that followed the killing of George Floyd in May will be in whether foundations and other donors continue the less restrictive approaches to grant making they adopted during the pandemic’s early weeks.