Man spends 4 years pretending to have an obsession with a very niche hobby just to get his father-in-law’s approval: ‘For the first year, we sat in agonizing silence during every family gathering. I was desperate’ – FAIL Blog

It would be weird if he now stated he stopped liking trains, maybe he can bring it up someday, after they have been friends for ages, and say something like ‘You know I started this hobby in the first place ‘cause I wanted you to like me, lol, and now I’ve grown to love it’. I mean, what’s not to love about it, right? You can always find a particular angle to something that feels attractive to you. I loved the researching train trivia part, lol. Also, he could try slowly displacing the friendship off the train tracks and bringing the father-in-law to some other common ground. Now that they have a stronger bond, maybe that will go well!