<b>this present world <b>- Possible meanings are 1) the temporary things of this world, "the pleasures and comfort of this world," or 2) this present life and safety from dying (Demas may have been afraid that people would kill him if he stayed with Paul.)
## so has gone ##
"so Demas has gone"
## Crescens went … and Titus went … ##
These two men had left Paul, but Paul is not saying that they also "love this present world" like Demas.