It's largely a reflection of how polarised the electorate is. The Tories have been persistently incapable of gaining a convincing majority for precisely that reason - and the divisions extend just as much to the people they rely on to govern. A thin majority and a divided cabinet means if the Tories actually commit to anything substantial, the party will tear itself apart.
Perhaps a more interesting question is: Would Labour suffer under the same divisions if they gained office? Possibly, possibly not.
On the one hand, the party relies on a coalition between young liberals in big cities and the south, and conventional working class voters in the north. Those groups do fundamentally disagree on things like Brexit, and Labour could succumb to similar tensions if it had a weak position in Parliament.
On the other hand, Labour has already fought its "civil war" over leadership between last spring and this year's election - and they had a clear victor. Nobody could at this point seriously challenge Corbyn's leadership, and that grants him greater authority within his party than May has in hers.