"[Like those before you]" meaning: from among the disbelievers. "[They were mightier than you in power]." Muhammad said: The meaning is: Allah has promised you for [your] disbelief as He promised those before you, "[So they enjoyed their portion, and you enjoyed your portion, just as those before you enjoyed their portion]."
Tafsir al-Kalbi: He says: You enjoyed your share of the Hereafter in this world, just as those before you enjoyed their share of the Hereafter, "[and you indulged]" in disbelief and denial, "[as they indulged]."
﴿كَالَّذِين من قبلكُمْ﴾ يَعْنِي: مِنَ الْكُفَّارِ ﴿كَانُوا أَشَدَّ مِنْكُم قُوَّة﴾ قَالَ مُحَمَّدٌ: الْمَعْنَى: وَعَدَكُمُ اللَّهُ على الْكفْر (ل ١٣٠) كَمَا وَعَدَ الَّذِينَ مِنْ قَبْلِكُمْ ﴿فَاسْتَمْتَعُوا بِخَلاقِهِمْ فَاسْتَمْتَعْتُمْ بِخَلاقِكُمْ كَمَا اسْتَمْتَعَ الَّذِينَ مِنْ قَبْلِكُمْ بِخَلاقِهِمْ﴾.
تَفْسِيرُ الْكَلْبِيِّ: يَقُولُ: فَاسْتَمْتَعْتُمْ فِي الدُّنْيَا بِنَصِيبِكُمْ مِنَ الآخِرَةِ، كَمَا اسْتَمْتَعَ الَّذِينَ مِنْ قَبْلِكُمْ بِنَصِيبِهِمْ من الْآخِرَة ﴿وخضتم﴾ فِي الْكُفْرِ وَالتَّكْذِيبِ ﴿كَالَّذِي خَاضُوا﴾.