The next verse (183) is also related with 'Istidraj'. It said:

وَأُمْلِي لَهُمْ ۚ إِنَّ كَيْدِي مَتِينٌ ﴿183﴾

"And I give them respite. Surely, My plan is firm."

That is, the disbelievers are left to enjoy their worldly life just for a while. Then, they shall be caught by punishment.