The transition that I went through was a team of 4 dev team + 4 leadership folks blow up into 18 tech + 5 leadership. It was more than 400% growth and happened in a matter of 20 days.
This was a team within a larger company but highly focused and close-knit, pretty much like an independent start-up. The 4 ppl team had existed pretty much from the beginning as long as 18 months and working 12-16 hrs and with a great attitude for a game changing concept within the company known for its culture.
When things had just started getting stable and these 4 ppl were looking for an advancement and not really keen on a more balanced life, the leadership decided to bring 18 more ppl into the team: few freshers and many managers/tech folks from another team whose business had just got shut down.
Worse the initial 4 ppl were made to report to these new ppl who had not even transitioned well into the business and team dynamics. Worse they turned out into bad managers - micro managing or may be we felt so as we knew more than them at that point of time.
3/4 of the initial team quit in a span of next 3 months. 50% of the new team too felt highly uncomfortable and moved on elsewhere. A huge code base, business knowledge and a great culture was taken down all in a span of 3-4 months. It took them many more months to get back in shape.
During my last week (the second one to quit, by now the team size too had come down to 10 tech + 4 leadership), the top leadership involved themselves to reason out:
- Growth should never be sudden, it should give enough time and resources for the team to ramp up the new member and the new member to get into the skin of the team.
- When people stop growing (not the growth in numbers), the organization stops growing. This was referring to the initial 4 people being bogged down by managers who were inserted into the ladder and who couldn't deliver. As much as possible grow your own people first.
- Leadership team had stopped connecting with the initial team suddenly. This disconnect created a sense of distrust and pseudo-hatred against the management (and kiddish enough against few of the new team members too.) Essentially the team was not prepared mentally for this growth and leadership did little help.
edit: added another reason