Charcoal, 16 bytes

Ｗ¬›×⌊θＬθ¹⊞υ⊟θＩＬυ 

Try it online! Link is to verbose version of code. Requires input sorted in descending order. Explanation:

Ｗ¬›×⌊θＬθ¹ 

While a (last) crowd member's threshold is not too high...

⊞υ⊟θ 

... move the member from the crowd to the helper pool.

ＩＬυ 

Print the final size of the helper pool.

Charcoal, 16 13 bytes

ＩＬ⊟⪪⭆Ａ›×ι⊕κ¹1 

Try it online! Link is to verbose version of code. Requires input sorted in descending order. Edit: Saved 3 bytes after following @DominicvanEssen's advice. Explanation:

 Ａ Input array  ⭆ Map over elements and join  κ Current index ⊕ Incremented × Multiplied by ι Current value › Is greater than ¹ Literal `1` ⪪ Split on 1 Literal string `1`  ⊟ Pop last element Ｌ Length Ｉ Cast to string Implicitly print