"be to blame for" 跟 "blame for"

"be to blame for" 跟 "blame for"

1.be to blame for
http://www.wordreference.com/es/translation.asp?tranword=be+to+blame+for+sth
be to blame for [be responsible for sth]

"Are Louis Van Gall's tactics to blame for Man United's scoring struggles?"  
曼聯的進球荒是否是因為Gall's的策略所導致的?

2.blame for
"Please don't blame Jill for it"
那件事別責怪Jill

問題:
2 "blame for"沒太大的問題, 大概就是 S+V+O, "A責怪B+for 什麼事"
1"be to blame for"就有點疑問了,
如果是我寫一樣的句子,我會寫成
"Are LVG's blamed for ManUni scoring struggles?"
我無法理解那個"to"怎麼來?是放了那個"to"後就有被動的意思了嗎?是否文法上有些單元可以協助解釋?