Here is what it looks like on my Xfce Manjaro system, for the sake of comparison:
Relevant entries from the default GRUB config:
/etc/default/grub
GRUB_TIMEOUT=10
GRUB_TIMEOUT_STYLE=menu
GRUB_DISTRIBUTOR="Manjaro"
GRUB_CMDLINE_LINUX_DEFAULT="quiet udev.log_priority=3"
# Uncomment to use basic console
GRUB_TERMINAL_INPUT=console
# Uncomment to disable graphical terminal
#GRUB_TERMINAL_OUTPUT=console
# The resolution used on graphical terminal
GRUB_GFXMODE=auto
# Uncomment to allow the kernel use the same resolution used by grub
GRUB_GFXPAYLOAD_LINUX=keep
# Uncomment and set to the desired menu colors. Used by normal and wallpaper
# modes only. Entries specified as foreground/background.
GRUB_COLOR_NORMAL="light-gray/black"
GRUB_COLOR_HIGHLIGHT="green/black"
# Uncomment one of them for the gfx desired, a image background or a gfxtheme
#GRUB_BACKGROUND="/usr/share/grub/background.png"
#GRUB_THEME="/usr/share/grub/themes/manjaro/theme.txt"
GRUB_THEME="/boot/themes/manjaro/theme.txt"
I don’t know how to restore the Manjaro theme but until then you can try this if you want something good for your grub. https://github.com/vinceliuice/grub2-themes.git
As previous posts have alluded to, it may be your display / hardware. What model Lenovo is it? By chance you can try @Aragorn’s workaround to manually specificy your display parameters, such as 1920x1080x32 (depending on your native resolution).
I tinkered around a bit, comparing the snippets of the /etc/default/grub files here posted with mine. Here is what I found:
The theme-less grub menu appears after I uncomment this line:
GRUB_TERMINAL_OUTPUT=console
Here is something even weirder. If I comment out that line, as in:
#GRUB_TERMINAL_OUTPUT=console
Then there wouldn’t even be a menu! Instead, it’s just the Lenovo splash screen, and that’s it. There wasn’t a boot menu.
Here is the strange part. Even though there wasn’t a boot menu, GRUB was still working in the background. I’m on a dual boot, so when I saw the Lenovo splash screen, I pressed “Down” then “Enter.” The system booted straight into windows 10, my second OS. If I press “Enter” without pressing the down key, I booted straight into Manjaro. It works as if the menu was there, just that it’s been overlaid by the splash screen.
What about when the GRUB menu displays, press C on your keyboard to drop down to a console.
Then run the command,
videoinfo
Other than checking what VBE modes are supported by your display (which based on the Lenovo specs appears to be 1920x1080x32), maybe review the following files and folder contents in case something was missed (even a small detail or mispelling)?
Have you tried installing grub-theme-manjaro and then do update-grub?
sudo pacman -S grub-theme-manjaro
When I f-ed up my partition and lost my grub theme, this fixed it for me.
Even in the usb installation media, it seemed strange. I mentioned just now about the lack of boot menu?
The user guide specifically mention that I’d see a menu asking you to choose “open source drivers” etc. I didn’t see that at all. It’s just a bunch of text loading, then I boot straight into the desktop.
The installation ISO should have the themed GRUB boot menu, yes. Seems like a very specific issue with your hardware but I can’t think of what it could be.
If we put on our detective hats, there’s enough evidence that this is hardware/BIOS related:
The issue arises during the menu (or lack thereof) from a live USB
No matter what type of combination of locating files and editing configs, there still remains a lack of a theme
System appears to be in order: packages are installed, config files are formatted correctly, no LUKS encryption is used on the system partition, yet the issue remains
Running videoinfo from the GRUB prompt does not yield a list of supported VBE modes, hence another indicator this is a hardware/BIOS issue
For comparison, my old 2012 netbook with a 10-inch screen, using LUKS encryption on the system partition, displays the theme’d menu properly (reading from /boot/themes/), and running videoinfo from the GRUB prompt yields a list of four different supported VBE modes.
Luckily, this only affects the GRUB menu upon booting up, and shouldn’t bear any problems once Manjaro is running.
UPDATE: You could try flashing your BIOS to the latest firmware, but it’s extra work and stress (and potential risk) for the sake of hopefully getting a theme’d GRUB menu, which isn’t even guaranteed with the latest BIOS update for your laptop.
If you give up now… then it means THEY win. 
Never!!! We can’t let them win!
