Results speak for themselves.
When Tun M caused a split in 1998 by sacking Anwar, UMNO lost 24.5% of UMNO seats in GE10 (UMNO lost 22 out of their previous 93 seats won in GE9) and lost Terengganu.
When Tun M next caused a split in 2007 by leading a campaign to remove Pak Lah because Pak Lah didn't listen to him, UMNO lost 27.5% of their seats (30 out of 119 UMNO seats which they previously won in GE11) and lost an additional 4 states - Penang, Perak, Selangor and Kedah.
From wining the biggest landslide ever in 2004 GE11, UMNO lost a staggering 27.5% of their seats and lost 5 states - and this allowed Pakatan to govern and build their funds, support base and strength.
Now Tun M is causing another split in 2015 by leading a campaign to remove Najib because Najib didn't listen to him, how many seats and states will UMNO lose in GE14?
GE10, GE12, GE14 - Tun M's causing splits seems to happen EVERY OTHER election.
And you blame Najib for weakening UMNO and BN?
I am sure you know who is the real underlying cause.
Note: The 1MDB issue is just a tool used by Tun M to attack Najib. Before Tun M used this as a tool, Pakatan had been using it for years and years and the effect was very limited. It is only when Tun M started using it that people started to beleive the worst - even though all the international auditors and the interim AG report could not find any money missing or stolen.
In 2008, do you remember what were the reasons why Pak Lah HAD to be removed and was corrupt to the core? What were those issues then since it was SO SERIOUS and what happened to those issues now?