[Python] why second for loop do not start from beginning

I have pairs of PDF files that I need to merge (each pair). The code works fine, but I don't understand why the second loop always starts with the second file of the pair. I thought it would start from the beginning. I was look at this Python - Why does the second for loop start from the second row, but still stuck. Is it same problem? I dont think so. I think it is somewhere here:

fileList1 = Path(folder).glob('*text1.pdf')
fileList2 = Path(folder).glob('*text2.pdf')

start code


#! python3
# merge PDF files based on a /numeric/string/ code in file name
# example1 r01_cz14_028_city_text1.PDF
# example2 r01_cz14_028_city_text2.PDF
import os
from pypdf import PdfWriter
from pathlib import Path

def mergeFiles(folder):

folder = os.path.abspath(folder) # make sure folder is absolute path

# make a lists
fileList1 = Path(folder).glob('*text1.pdf')
fileList2 = Path(folder).glob('*text2.pdf')

outputName = ''
outputFolderPath = folder + '\\somefolder'
p = Path(outputFolderPath)
if not p.exists():
os.makedirs(outputFolderPath)
n = 0
folderLenght = len(folder)+1
fileNameArea = folderLenght+12
print(f'Adding files in {outputFolderPath}...')


for filename1 in fileList1:
n += 1

# match test = SECOND LOOP
for filename2 in fileList2:
string1 = str(filename1)[folderLenght:fileNameArea].lower()
string2 = str(filename2)[folderLenght:fileNameArea].lower()

# Add choosen files in this folder to the PDF file by string.
if string1 == string2:
outputName = 'D' + \
str(filename1)[folderLenght + 4: folderLenght + 6].upper() + \
'_' + str(filename1)[folderLenght + 9: folderLenght + 12] + \
'_text3.pdf'

outputName = outputFolderPath + '\\' + outputName
file1Out = str(filename1)
file2Out = str(filename2)
pdfMerge([file1Out, file2Out], outputName) # function, works fine

break

print (f'{n}. {os.path.basename(outputName)}')

print('Done.')

mergeFiles('X:\\MergeTest')

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