According to The Sun political editor, Tom Newton Dunn

Raab is a close ally of UK PM May and held the post for the Minister of State for Housing and Planning before this. The Times is also reporting a similar story now that the UK government has officially appointed Raab for the role.

In essence, it'll likely mean that May will face less hardship in pushing through with her proposals on Brexit than she did with Davis. Question is, will this spark further resignations? Time will tell.