Vendors have been asking them to make a decision. Some have probably already pulled out. Some of them don't want to risk the travel, or even if they're comfortable traveling they don't want to spend the money and time if attendance will be low. TBA attendance has already been dropping for years, and the exhibit hall has been smaller and emptier every year.
Attendees have been asking them for information, or asking for refunds. They don't want to travel, they don't feel safe, or they just don't know what's expected of them this fall and don't want to commit to a trip at the end of July. At one point, our district had re-scheduled graduation to that Saturday and was expecting me to have the band there.
Maybe the city/county/state officials have shared some "unofficial" information or hinted at things to come. Our district admins always seem to know at least a week in advance what the county is going to announce. More than once they've given me advance warning in a private off-the-record conversation.
Maybe TBA has some contracts with a 60 day withdrawal clause. Perhaps at this point, they can still get out of the contracts, but if they wait another week or two they're on the hook for the full amount. With vendors pulling out, attendees asking for refunds, and likely lower income from on-site registration, paying for the convention could easily bankrupt the whole organization.
TBA made a business decision. It has nothing to do with their "balls" or lack thereof. You can still go down and eat some overpriced tex-mex while sweating by the river if you really want to.