Throughout my short 5 years of working in the corporate world...I've seen and met all kinds of politics and backstabbers...

1) There are those who are of the same level as you with same job scope (can be considered your teammates) but they are not as capable as you or they may be plain lazy or even due to some circumstance like pregnancy they need to be away....so they are afraid that you may outperform and even replace them or make them redundant...they will form gangs against you and force you to leave by making you look bad...and in the event they need to go for maternity they may recommend a friend into the company to provide cover for her and at the same time make sure you don't make her position redundant so that when she comes back from maternity her job is still there.....

2) Sometimes you may have good relationship with the higher management... your teammates may not like it...they may be afraid that you may tell on them e.g. tell higher management about their shortcomings etc...so they gang up against you and give you the cold shoulder...sabotage your work etc....force you to leave ultimately...

3) You may have a boss who is useless and don't know much of the work...so he depends a lot on his subordinates....so when these subordinates dun like you...they backstab you and boss will listen to them less they get angry and don't do their work which will leave the boss helpless

4) Company may be going into retrenchment exercise so everyone around is a threat...so these backstabbers will try to play politics and force one another off the company...afterall less people mean less competition for the jobs remaining after retrenchment...