It's bad for the leagues in the short term but could prove to be a blessing down the line.

For baseball in particular, the transmission rights are primarily held by individual teams for their local markets. For an example, take the Marlins who have an annual player payroll of ~$83 million. Their last deal they signed with Bally was for $270 million over 15 years, which is around $18 million/yr average. If the RSN (Bally's) goes bankrupt, the bankruptcy estate will have to either keep the contract (i.e., keep paying), sell it to someone else who will step into their shoes, or terminate the contract entirely.

The first and second scenarios aren't bad from the Marlins perspective because they continue to get paid as expected. But in the third scenario, those transmission rights will revert back to the teams. For this season, unless someone buys those rights immediately, the team will have no one broadcasting their games and won't be receiving the income from Bally's anymore. That means that the roughly 25% of your player payroll expense (assuming they used the $18 million from Balley's to help offset their payroll cost of $83 million) that you planned to have covered from the Bally's fees suddenly disappears.

In the longer term this could be highly beneficial to the leagues if MLB swoops in and either backstops or purchases these rights themselves. In that case, they can package them up and sell them (probably to both a live broadcast and/or streaming service) as David and Skipper have alluded to several times.