So, why are thargoids only now interested in probes, sensors etc?

[Connolly91]

When previously, one could carry them and be hyperdicted and left alone?

This really ruins the 'emergent' nature of these encounters as clearly Frontier simply hadn't flipped the switch on their end to enable interaction.

 

[Ambroza]

We don't know. There could be a perfectly logical reason why Thargoids are now pursuing their property with increased tenacity, but we don't know nearly enough about them or their motivations to determine what it is yet. Clearly, something has changed on their end.