“If you can’t beat them, join them” is a summary of Nabih Berri’s policy towards Hezbollah. Berri, who started his career with the CIA, always felt AMAL had certain parental privilege over Hezbollah, based on the fact that Hezbollah was born from the ranks of the Shiite movement AMAL. Their relation always passed through troughs and peaks, from militarily clashing in 1980s over influence within the Shiite sect, to being completely inseparable now.
Now both parties collude to politically destroy any independent political Shia voice, and win all the Shia parliament seats and the official state appointments. Historically, AMAL represented an extension of the Syrian influence, while Hezbollah represented the Iranian one, so their relation was very much facilitated by how well these two regional bosses were getting on.