failed to load podspec - invalid podspec file syntax error, unexpected ']' - Unknown command: `xxx` Did you mean: deintegrate?

I don't know how this happened but I suddenly started getting this error about multiple podspec files (DoubleConversion, Folly, glog) when I try to pod update:

Commandline output:

Updating local specs repositories

Analyzing dependencies

Fetching podspec for DoubleConversion from ../node_modules/react-native/third-party-podspecs/DoubleConversion.podspec

[!] Failed to load 'DoubleConversion' podspec:

[!] Invalid DoubleConversion.podspec file: syntax error, unexpected ']'.

from /Users/me/ReactNativeProjects/myProject/node_modules/react-native/third-party-podspecs/DoubleConversion.podspec:1

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[!] Unknown command: DoubleConversion,
Did you mean: deintegrate?

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Podfiles somehow seem to be corrupted (content replaced) and seemingly all have the same content. Content of DoubleConversion podspec file is below:

[!] Unknown command: DoubleConversion,

Did you mean: deintegrate?

Usage:

$ pod COMMAND

  CocoaPods, the Cocoa library package manager.

Commands:

+ cache         Manipulate the CocoaPods cache
+ deintegrate   Deintegrate CocoaPods from your project
+ env           Display pod environment
+ init          Generate a Podfile for the current directory
+ install       Install project dependencies according to versions from a
                Podfile.lock
+ ipc           Inter-process communication
+ lib           Develop pods
+ list          List pods
+ outdated      Show outdated project dependencies
+ plugins       Show available CocoaPods plugins
+ repo          Manage spec-repositories
+ search        Search for pods
+ setup         Setup the CocoaPods environment
+ spec          Manage pod specs
+ trunk         Interact with the CocoaPods API (e.g. publishing new specs)
+ try           Try a Pod!
+ update        Update outdated project dependencies and create new Podfile.lock

Options:

--silent        Show nothing
--version       Show the version of the tool
--verbose       Show more debugging information
--no-ansi       Show output without ANSI codes
--help          Show help banner of specified command

Any idea of how this happened and how to fix them? (cocoapods-1.8.4)

p.s. I did fix the problem just by visiting the related GitHub pages and copying the corresponding podspec contents from there. I just can't understand why/how this happened.