Just wonder, why do some guys have no respects for girls, play
with their emotions and think it's easy to get into their pants by
using mind games and some shitty tricks?
The guys you were referring to, have only sex or at the very
least some making out time, as their goal. As such they will resort
to any tactics to achieve the goal. Mind games, playing the part of
a caring, sensitive male, and other 'tricks' are just some ways to
hook the girl.
Sex as the goal is likely to stem from the fact that
guys have generally a higher sex drive than ladies, i.e. they get
horny fast and with more frequency.
On your personal experience, you did the right thing for
yourself by walking away. You do not want a no-strings attached
type of relationship with your crush, and he was looking for
nothing more than a fling. Both your aims do not tally, but you are
probably at the losing end if the situation goes on further. If you
still like him, you may try talking to him about his behaviour (his
leering and sexually-fuelled messages) and how it makes you
uncomfortable.
Cheers