octavian ceasar and his 2nd triumvirate (1 Viewer)

[ellirene]

someone, i dont understand WHY octavian included lepidus and antony in the 2nd triumvirate?
i mean!, they were two very powerfull men, couldnt they over throw him?
and why on earth did they outrule the senate? what did the senate even do?
i seriously dont understand any of this :s
any help would be appreciated

oh and also;
i dont understand this:
Antony's will was the final straw.

- what else happened for that to be the 'final' straw?