Why does Dumbledore make Snape DADA teacher?

[ghost_silver_wolf]

No: HPFGUIDX 158414

I believe that Dubledore's purpose for Snape would be finished by
the end of the year.  Dumbledore knew about Voldermort's curse on
the DADA job so why would he put Snape in that position if he didn't
want to get rid of him, within a year?

Though it does bring up the question, why did Dumbledore hire
Quirrell, Lockhart and Lupin, knowing he was putting them at risk?

"ghost_silver_wolf"