Lombardi was still trying to win in 2015. He wasn't concerned with the future. They missed the playoff by a couple points, and the glory days were still too recent. Despite falling flat in 14-15, there was still that just get in/cockroach aura around the team. He was also trying to take advantage of what at the time was still a good contract for Kopitar. Had to strike while that iron was hot. Can't give away one last $6.8m season.
The 15-16 team had the highest point% of any Kings team since 90-91. They were 4th overall the day Kopitar signed his extension. Then fell to 13th overall the rest of that season, while Anaheim had the best points% from 1/17/16 to the end of the season. DL was still all in.
Hell, the 14-15 team had the most regulation wins of any Lombardi-era Kings team. They had the 4th best home record in the league that year too.
Miller did enough in Boston to be left exposed in the expansion draft. Jones has little value to the Kings, and all he brought the Bruins is a 4th liner, and a guy picked in the 1st round who hasn't done anything. He wasn't in a position to be demanding anything with Jones. With the way Lombardi was drafting, there's no guarantee whoever the Kings would've taken in 2015 is the guy everyone wants. To not get what Lombardi was doing at the time, it's overthinking the situation. He was still in win mode, trying to take advantage of a cheap Kopitar, and was able to replace Williams(I know, I know, nothing can replace that dreamboat), for the same amount of money, without subtracting anything from the NHL roster, other than the backup goalie who was an RFA and wasn't going to re-sign here.
Neither Barzal or Connor play regularly until Oct 2017, which doesn't help Lombardi in Oct 2015. Sure, the run was already over. The run was over the day Lombardi couldn't let go of Richards. But that's not how he saw it. He still saw a team that he thought had whatever "it" is. Again, 4th overall on 1/16/16, with no reason to think Anaheim, who were sitting 21st on that same day, would eventually catch and pass them in the standings. That's not McSorley/Sandstrom. The Kings finished 5th worst in 93-94.