The concept behind Lira was to have a fast, small, highly automated submarine to operate as an "interceptor" against NATO SSBNs. There was also an "AWACS" type sub being developed in paralel to the "interceptors" - Afalina. As such Lira had minimal crew with high automation, high energy density power plant, lightweight titanium hull. The idea was to have multiple crews per same sub, with all repairs and maintenance being done at port, majority of compartments would be unmanned during the sorties.
As the SLBMs got longer and longer ranges, pushing SSBN patrol areas further and further from USSR, the concept has changed, fast subs were tasked with chasing after fast surface action groups, while "AWACS" sub project was repurposed to hunt SSBNs close to the NATO shores.
You could see one of the later versions of this "AWACS" sub here:
The legacy of this project lives on in Akula series (which were originally developed under the guise of a modified "AWACS" sub project, that is where Akula got it's "cheeks") and the Yasen class (which received the sonar).