PS 2020 exporting GIF creates large file

Hello, I'm working on a GIF animation for email.

Here are my specs:

1. Import jpg image sequence into After Effects
2. RotoBrush to remove background
3. Add cartoon effect
4. Import .mov file from Adobe Stock to use as cloud background
5. render out as .mP4

Ok, so it's 2880x1920 and almost 9mb.

1. Import into PS v22.11 into a Timeline
2. Image > Image Size let's make it smaller

Ok, it's now just over 1mb. Great!

Let's continue.

1. File > Export > Save for Web (Legacy)

Suddenly, the file size expands enormously.

Save...

Now the file size is 16.8mb, which is far too large for my purposes. Also, most times, these GIFs DO NOT PLAY in the email, which is the whole point of this excercise. They play on my computer, but not in emails.

Any help would be greatly appreiated.

Cheers!