How can the sequence of events be reconciled in verses 54 and 55 of Surat Al-Baqarah, where the taking of the calf precedes the thunderbolt incident, and verse 153 of Surat An-Nisa, which mentions the thunderbolt incident before the taking of the calf?

The conjunction "thumma" (then) does not always denote temporal sequence; rather, it may indicate a conceptual or informative sequence, mentioning the most important first, then what follows in importance, as Sībawayh mentioned. It may also come merely for the sake of sequencing in mention and gradual progression, without considering temporal delay; indeed, the second event may precede the first temporally, as in "Indeed, among those who achieved prominence, then his father achieved prominence, then his grandfather had already achieved prominence before that." And "thumma" may be resumptive, where the action after it has already occurred before the first action. This meaning is clear in verses such as: ﴿فَإِذَا أَفَضْتُمْ مِنْ عَرَفَاتٍ... ثُمَّ أَفِيضُوا﴾ (And when you depart from 'Arafāt... then depart) [Al-Baqarah/198-199], and ﴿فَلَا اقْتَحَمَ الْعَقَبَةَ... ثُمَّ كَانَ مِنَ الَّذِينَ آمَنُوا﴾ (But he has not attempted the arduous pass... then he was among those who believed) [Al-Balad/11-17], where "thumma" denotes delay in rank, not in time. In the context of the verses in Sūrat Al-Baqarah and An-Nisā', "thumma" indicates the sequencing of events according to importance and suitability, not temporal order.