Actually he had a lot of guts to stand up against all of them and come out on top with his morals intact and stronger support than before. They might resent him but he's the one dragging his party forward single-handedly despite ubiquitous criticism from the media. He might not be loud but he's definitely not spineless.
Edit: Speaking of spineless, Cameron promising a referendum in the first place was a cheap move to take back votes from UKIP, and did a runner when the vote didn't go his way. May U-turned on Brexit, claimed she wouldn't call a snap election, u-turned on her dementia tax and pretty much gave up on trying to win on domestic policy and took refuge under the umbrella of "Brexit means Brexit" whatever that means. Yet people buy this nonsense about being stable when she flip-flops on major issues at the drop of a hat.