Following the fuel: how the world tracked the B-2 diversion flights

The tankers were visible but the bombers weren't:

> At no point were the B-2s visible on Flightradar24, they did not broadcast ADS-B or Mode S, the signals our network is capable of receiving. We’re often asked why military aircraft show up via ADS-B. It’s because they want to.

Why show the tankers though? Why the need for the westward diversion flight when they could have all stayed hidden?