We have 3 files, translated from english text that were encrypted from the same key. Since they are originally english, we can have a general idea of the key by counting the frequency of each character.
cat found* | grep -o . | sort | uniq -c

| letter | ** count** | ** frequency** | ** equals** | 
|---|---|---|---|
| P | 2 | 2.8409091e-3 | Z | 
| H | 4 | 5.6818182e-3 | Q | 
| R | 4 | 5.6818182e-3 | X | 
| O | 12 | 0.017045455 | J | 
| I | 19 | 0.026988636 | K | 
| F | 28 | 0.039772727 | V | 
| A | 55 | 0.078125 | B | 
| L | 60 | 0.085227273 | P | 
| E | 64 | 0.090909091 | Y | 
| K | 67 | 0.095170455 | G | 
| X | 71 | 0.10085227 | F | 
| T | 75 | 0.10653409 | W | 
| Y | 84 | 0.11931818 | M | 
| M | 86 | 0.12215909 | U | 
| W | 129 | 0.18323864 | C | 
| V | 130 | 0.18465909 | L | 
| Z | 132 | 0.1875 | D | 
| D | 210 | 0.29829545 | R | 
| C | 227 | 0.32244318 | H | 
| G | 227 | 0.32244318 | S | 
| N | 240 | 0.34090909 | N | 
| B | 246 | 0.34943182 | I | 
| U | 257 | 0.36505682 | O | 
| J | 301 | 0.42755682 | A | 
| Q | 340 | 0.48295455 | T | 
| S | 456 | 0.64772727 | E | 
| TOTAL | 704 | 1 | 
Single Letter Counts and Frequencies:
ciphertext = "<<concatanted>>"
password = "KSVVW BGSJD SVSIS VXBMN YQUUK BNWCU ANMJS"
order = ['E','Q','T','S','O','R','I','N','H','C','L','D','U','P','M','F','W','G','Y','B','K','V','X','Q','J','Z']
 
def letter_order(string):
    counts = [0]*26
    order = ""
    for i in string:
        c = ord(i.upper()) - 65
        if -1 < c < 26:
            counts[c] += 1
    for i in range(26):
        m = (0,0)
        for j in range(26):
            if counts[j] > m[1]:
                m = (j,counts[j])
        counts[m[0]] = 0
        order += chr(65+m[0])
    return order
 
def genkeys(order):
    if len(order) == 0:
        return [""]
    keys = []
    for i in range(len(order[0])):
        if len(order[0]) > 1:
            neworder = [order[0][0:i] + order[0][i+1:]] + order[1:]
        else:
            neworder = order[1:]
        for j in genkeys(neworder):
            keys.append(order[0][i]+j)
    return keys
 
def solve(s,orig,ceasar):
    solved = ""
    for i in s:
        if 64 < ord(i.upper()) < 91:
            solved += orig[ceasar.find(i.upper())]
    return solved
 
cipherorder = letter_order(ciphertext)
for i in genkeys(order):
    print(i)
    print(cipherorder)
    print(solve(password, i, cipherorder))EQTSORINHCLDUPMFWGYBKVXQJZ
SQJUBNCGDZVWMYTXKELAFIOHRP
WELLDONETHELEVELFOURPQSSWORDISBRUTE
The password is BRUTE