9-1-1 star Oliver Stark candidly discusses how Buck's view of relationships has evolved. When the hit Fox procedural first started, Evan "Buck" Buckley was introduced as someone who was very much into casual relationships and one-off hookups. But as 9-1-1 moved forward, so did Buck. He grew attached to Abby (Connie Britton) and became more willing to change the person he used to be.
https://screenrant.com/9-1-1-show-season-6-buck-lightening-relationships-change/