Before Jesus heads out to Bethany, Jesus talks about how he would wake Lazarus from sleep, and by sleep, Jesus means death. When the disciples were thinking about sleeping as in snoring in bed, Jesus clarified and stated that Lazarus is dead (11:14).
And then Jesus made a noteworthy comment -- Jesus states that He is "glad for [the disciples'] sakes that [Jesus] was not there, that [the disciples] may believe" (11:15). At first glance that sounds like a strange comment in regards to someone's death, but at the same time, Jesus was not insensitive since he later wept. So what did Jesus mean and why did he make this comment in the first pace?
Because Jesus wept in response to seeing Jesus's death (as stated a few verses later), Jesus was "glad" not because someone died. Rather, Jesus is glad for the disciples, and from an examination of the Interlinear (and as noted by WYC), the gladness is for the chance of the disciples (and Mary and Lazarus) to believe in Jesus even more (compared to already being there). In other words, Jesus was not glad for the suffering that happened but glad for the opportunity for the disciples. Additionally, unlike most human delays, note that when Jesus does delays, he has an actual plan to resolve the problem (especially with powers that other humans don't have) and still cares/weeps for the victim.
However, Thomas (one of Jesus's disciples) struggled with doubt. He thought that they would die with Jesus. Even with the doubts (especially with knowing that Lazarus is dead and that Jesus isn't there), they still went with Jesus to Bethany. Likely because they knew from experience how important Jesus was.
Today, often times God brings out good in the midst of bad events, and sometimes, delays lead to opportunities for God to create even greater good than we could imagine (not just for us, but also for our friends). Even then, the question of God in the midst of suffering is not only one of the most common questions from believers and non-believers, but also one of the hardest. Because of God's plans to bring out great good for us and friends from said suffering and ability to execute said plans (as we'll see later), we can still trust God, even with lingering doubts (just like what Thomas did), because of the very significant redemption that Jesus did on the cross.