The great thing about open source software is that if you want to make allegations of spying or tracking by governments, you can also provide a link to the code that allows it to happen. The only way Tucker's Signal messages were hacked is that the US has some pegasus grade 0day on either Tucker's phone, or his contact in Russia (likely the ladder). I'm near 100% certain Signal's E2EE hasn't been broken, it's much more likely the Russian's phone got owned because the US has an interest in knowing who is communicating with Putin. Another scenario is that Russia gave the info to the US. Why would they care if this info leaked out? What would they have to lose?